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QP44  .L83  Directions  for  labor 


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in  tije  Citp  of  i^eto  gorfe  ^^>^ 

COLLEGE  OF  PHYSICIANS 
AND   SURGEONS 


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DIRECTIONS 


FOR 


Laboratory  Work  in  Physiology 


FOR  THE   USE  OF 


MEDICAL  STUDENTS 


WARRKN  P.  LOMBARD,  A.B.,  M.D. 

PROFESSOR    OF    PHYSIOLOGY,    UNIVERSITY    OF    MICHIGAN 


GEORGE  WAHR,  Publisher 

ANN  ARBOR 


Copyright,  1906 

BY 
GEORGE  WAHR 


J   If  Uxii^'O*^ 


G^  1=4-4- 


The  Ann  Arbor  Press,  Printers 


PREFACE. 

The  course  which  is  here  outHned,  is  the  result  of  four- 
teen years  of  laboratory  work  with  medical  students.  It  con- 
tains only  such  experiments  as  can  be  actually  performed 
by  the  student  himself  in  the  eight  weeks  allotted  to  the  work 
of  experimenting,  and  like  every  such  course  necessarily 
omits  manv  experiments  which  would  be  interesting  and 
instructive.  It  is  supplemented  by  demonstrations  by  the 
instructors  and  by  such  students  as  show  special  aptitude 
for  and  have  the  time  to  devote  to  such  work. 

The  experiments  are  arranged  so  as  first  to  teach  the 
student  the  use  of  the  graphic  method,  time  recording  in- 
struments, and  the  electrical  apparatus  employed  for  exci- 
tation. At  the  same  time  he  becomes  acquainted  with  the 
general  physiology  of  striated,  non-striated,  and  heart  mus- 
cle and  of  the  nerves  of  the  frog.  He  then  studies  the  reac- 
tion of  his  own  muscles  and  nerves  to  various  forms  of 
electrical  excitation.  A  little  more  than  one  half  of  the 
course  is  thus  spent,  and  at  the  end  of  this  time  the  student 
is  prepared  to  take  up  the  study  of  the  subjects,  so  impor- 
tant to  every  medical  man,  cen  ral  nervous  processes,  the 
circulation  and  respiration.  Only  two  experiments  are  made 
on  the  mammal,  but  in  these  the  circulation,  respiration  and 
peristalsis  are  studied.  Five  of  the  eleven  experiments  on 
ihe  circulation  are  made  on  the  human  subject.  It  is  be-^ 
lieved  that  the  medical  student  should  as  far  as  possible  study 
the  Physiology  of  man.  and  it  is  hoped  that  other  exper- 
iments of  this  character  will  be  developed  in  the  near  future 
and  be  substituted  for  those  now  made  on  animals.  It  is 
needless  to  say  that  the  frogs  are  rapidly  killed  before  being 
used,  and  that  the  mammals  employed  are  thoroughly  an- 
aesthetized by  the  student,  under  the  direction  of  an  in 
s  true 'or. 

xA-s  most  of  the,  students  taking  the  course  have  no 
knowledge  of  physiological  methods,  the  directions  for  the 
work  have  been  made  as  explicit  as  possible  with  the  object 


IV  "  PREFACE 

of  saving  time.  Nevertheless,  the  harm  which  comes  from 
machine-Hke  work  is  fully  recognized,  and  students  are  en- 
couraged to  cultivate  independence,  and  permitted  to  per- 
form the  experiments  in  other  ways  than  those  called  for 
in  the  notes.  They  are  made  to  feel  that  the  capacity  to 
observe  and  correctly  interpret  the  results  of  an  experi- 
ment, is  of  even  more  importance  than  the  ability  to  make 
an  experiment  successfully,  and  that  one  who  has  trained 
his  powers  of  observation  and  has  learned  to  accurately 
report  the  phenomena  he  has  witnessed,  can  make  a  relia- 
ble diagnosis  and  keep  a  trustworthy  case-book.  As  the 
students  at  this  University  take  a  special  course  in  Physio- 
logical Chemistry,  the  work  of  this  laboratory  deals  only 
with  the  physical  problems  met  in  the  body.  For  similar 
reasons  but  little  attention  is  given  to  the  special  senses. 

It  gives  me  great  pleasure  to  acknowledge  the  valuable 
aid  of  my  past  and  present  Assistants,  Prof.  Sidney  P. 
Budgett,  Dr.  Augustus  E.  Guenther,  Dr.  G.  G.  Crozier, 
Prof.  Wilbur  P.  Bowen,  Dr.  Carl  J.  Wiggers,  Mr.  Fred  M. 
Abbott,  and  Mr.  Neal  N.  Wood,  in  developing  the  methods 
employed  in  this  course. 

Warren  Pi^impton  Lomdard. 
Physiological  Laboratory, 

University  of  Michigan, 
August  1st,  1906. 


CONTENTS. 

General  directions.  Instruments,  etc..  to  be  purchased 
by  students.  List  of  apparatus  to  be  supplied  by 
the   laboratory.       ^ xv 

Experiment  I. 

Extensibility  and  Elasticity  of  a  steel  spring.  .        .        i 

Mounting  of  curves. 
The  student's  notes. 

Experiment  II. 

Extensibility  and  Elasticity  of  frog's  muscle.  .        .        7 

a.  Experiment. 

b.  Plotting  of  curves. 

Experiment  III. 

Response  of  muscle  to  making  and  breaking  induction 
shocks  of  various  strengths,  and  use  of  the  short- 
circuiting  key.  13 

(Some  facts  regarding  the-  induction  apparatus.) 

a.  Response  to  making  and  breaking  shocks  of  in- 
creasing strength. 

b.  Use  of  the  short-circuiting  key. 

Experiment  IV. 

Relation  of  amount  of  load  to  height  of  lift  and  quan- 
tity of  work  done.  21 

a.  Experiment. 

b.  Plotting  of  curves. 

Experiment  V. 

Time  relations  of  myogram 25 

a.     Influence  of  rate  of  drum  on  form  of  myogram. 


VI  -  CONTENTS 

b.  Time  relations  of  myogram. 

c.  Measurement    of    records    and    computation    of 
time  intervals. 

Experiment  VI. 

Genesis  of  tetanus.        .        .        .        .        .        .        .        -3^ 

a.  Summation  of  two  contractions. 

b.  Incomplete  tetanus  and  complete  tetanus. 

c.  Complete   tetanus   obtained    with   automatic   in- 
terrupter. 

(Electrical  connections  in  primary  circuit  of  induc- 
tion apparatus.) 

d.  Fatigue  caused  by  tetanus. 

Experiment  \'II. 

Independent  irritability  of  muscle.     .        .        .        .        -37 
(Method  of  pithing  frog,  and  of  injecting  curara.) 

Experiment  VIII. 

Isolated  conduction  in  muscle.  .        .        .        .        •     43 

(Method  of  unipolar  excitation.) 

Experiment  IX. 

Contractions  of  non-striated  muscle.  47 

a.  Time  relations  of  the  myogram. 

b.  Rate  required  to  tetanize. 

c.  Spontaneous  contractions. 

Experiment  X. 

The  frog's  heart ;  its  structure  ;  the  relative  time  of  ac- 
tion of  the  different  parts 51 

a.  (jross  anatomy  of  frog's  heart. 

b.  Origin  and  course  of  the  wave  of  contraction. 

1.  Inspection. 

2.  The  myocardiogram. 


CONTENTS  ':  vii 

Experiment  XI. 
Refractory  period  and  compensatory  pause.  ,        .      57 

Experiment  XII. 

Response  of  resting  heart  to  stimulation  by  induction 

shocks 61 

a.  Myogram  of  heart  muscle. 

b.  Ijowditch's  staircase. 

c.  All  contractions  maximal. 

d.  Effect  of  frequent  stimuli. 

Experiment  XIII. 

Location  of  a  few  motor  points  on  the  human  arm.        .      65 
(The  more  efficient  pole  of  an  induction  coil.) 

Experiment  XIV. 

Response  of  human  muscle  to  separate  induction  shocks 

and  to  a  tetanizing  current.  .        .        .        -71 

a.  Making  and  breaking  induction  shocks  of  var- 
ious strengths. 

b.  Tetanizing  current. 

Experiment  XV. 
Galvani's  experiment. y"] 

Experiment  XVI. 

Polarization  of  electrodes. 81 

a.  Polarizable  electrodes. 

b.  Non-polarizable  electrodes. 
(Pfluger's  Law.) 

Experiment  XVII. 

Response  of  nerve  to  opening  and  closing  of  the  direct 
battery  circuit,  with  currents  of  various 
strengths. 8? 


viii  CONTJiNTS 

Experiment  XVIII. 
vStimulation  of  human  nerves  by  the  direct  current.        .     9T 

Experiment  XIX. 

Influence  of  the  direct  current  on  the  irritability  or  hu- 
man nerves.  •        •     97 

Experiment  XX.    . 

Currents  of  rest  and  action 103 

a.  Current  of  rest  detected  by  a  rheoscopic  frog 
preparation. 

b.  Current  of  action  detected  by  a  rheoscopic  frog 
preparation. 

Experiment  XXI. 

The  reflex  frog 107 

a.  Time  of  recovery  from  shock. 

b.  Spread  of  reflexes. 

c.  Are  reflexes  purposeful? 

d.  Reflex  time. 

e.  Spasm    of    muscles    versus    coordinated    move- 
ments. 

Experiment  XXII. 
Reaction  time  for  sound.  113 

Experiment  XXIII. 

The  knee-jerk  as  modified  by  reenforcing  and  inhibiting 

influences. 117 

a.  Minimal  blow  necessary  to  excite. 

b.  Record  of  normal  knee-jerk. 

c.  Motor  reenforcements. 

d.  Reenforcement  by  sensory  stimuli. 

e.  Psychic  reenforcements. 


CONTENTS  IX 

Experiment  XXIV. 

Conditions  determining  the  blood  pressure  and  the  out- 
put of  the  ventricle -125 

Porter's  artificial  circulation  apparatus. 

a.  Effect  of  changing  peripheral  resistance. 

b.  Effect  of  changing  rate  of  heart  beat. 

c.  Effect  of  changing  the  volume  pumped  per 
beat. 

d.  Record  of  the  pulse  under  different  condi- 
tions. 

e.  Comparison  of  arterial  and  ventricular  pulse 
curves. 

f.  Effect  of  lesions  of  heart  valves. 

Experiment  XXV. 

Circulation  and  respiration  of  the  mammal.  .  .  .133 
(Schedule  of  work.  List  of  apparatus.  Directions 
to  student  caring  for  apparatus.  Directions  to 
Assistant.  Anaesthesia.  Directions  to  anaes- 
thetizer.  Operation  for  isolation  of  the  carotid 
and  vagus.) 

a.  Measure  of  blood  pressure  in  the  carotid. 

b.  Maximal  and  minimal  blood  pressures. 

c.  Excitation   of  the  peripheral   end  of  the   right 
vagus. 

d.  Record  of  respiration  with  pneumograph. 

e.  Excitation  of  central  end  of  vagus. 

f.  Excitation  of  peripheral  end  of  left  vagus. 

g.  Excitation  of  sciatic  nerve. 

h.     Blood  pressure  during  asphyxia, 
i.     Elasticity  of  lung  tissue. 

Experiment  XXVI. 

Circulation    and    respiration    of    the    mammal    contin- 
ued.   149 

a.  Excitation  of  right  depressor  nerve. 

b.  Excitation  of  left  depressor  nerve. 

c.  Tracheotomy  and  artificial  respiration. 


X  CONTENTS 

d.  Current  of  action  of  the  heart. 

e.  Observation  of  exposed  heart  during  vagus  ex- 
citation. 

f.  Tension  of  ventricle  during  systole  and  diastole. 

g.  Observation    of   the    changes    in    heart    during 
death  from  asphyxia. 

h.     Innervation  of  diaphragm  by  the  phrenic  nerves, 
i.     Peristalsis  of  intestine. 

Experiment  XXVII. 

Carotid  pulse  in  man 155 

a.  Form  of  the  pulse  curve. 

b.  The  pulse  rate. 

c.  Duration  of  systole  and  diastole. 

d.  Effect  of  exercise. 

Experiment  XXVIII. 

The  radial  pulse  studied  by  the  tambour  method.  .        .159 

a.  Form  of  radial  pulse. 

b.  Postponement  of  the  radial  pulse. 

Experiment  XXIX. 

The  radial  pulse  as  recorded  by  the  Jacquet  Sphygmo- 

graph 163 

a.  Normal  curves  and  effect  of  position  of  body. 

b.  Effect  of  compressing  brachial  artery. 

c.  Effect  of  deglutition. 

d.  Effect  of  inhalation  of  Amyl  Nitrite. 

e.  Valsalva's  experiment. 

f.  Aliiller's  experiment. 

Experiment  XXX. 

Capillary  circulation  in  the  web  of  the  foot  of  a  frog  169 

I.  In  small  artery. 

II.  In  small  vein. 

III.  In  capillaries. 

IV.  Vaso-motor  action. 

V.  Diapedesis. 


CONTENTS  XI 

Experiment  XXXI. 

Measurement    of    human    blood    pressure    in    different 

positions.  173 

a.  The  systolic  pressure. 

1.  Gsertner's  Tonometer. 

2.  The  Riva-Rocci  Sphygmomanometer. 

3.  Erlanger's  Sphygmomanometer. 

b.  The  Diastolic  pressure. 

Experiment  XXXII. 

The  normal  sounds  of  the  heart 179 

a.  Auscultation  over  the  lower  part  of  the  chest. 

b.  Auscultation  over  the  base  of  the  heart, 

c.  Time  relations  of  heart  sounds  and  pulse. 

•  Experiment  XXXIII. 

Thorasic  and  abdominal  movements  in  respiration.        .    185 

a.  Normal  record. 

b.  Effect  of  using  the  voice. 

c.  Inhibitory  effects  of  swallowing. 

d.  Effects  of  effort. 

e.  Relation  of  rate  of  respiration  to  rate  of  heart. 


ILLUSTRATIONS 

1.  Apparatus  for  recording  the  extensibility  and  elas- 

ticity of  a  steel  spring. i 

2.  Apparatus  for  recording  the  extensibility  and  elas- 

ticity of  a  frog's  muscle 7 

3.  Apparatus  for  recording  contractions  of  a  frog's 

muscle,  excited  by  induction  shocks.  .        -13 

4.  Curve  of  lift  and  work 21 

5.  Apparatus   for  automatically   exciting  muscle,  by 

letting  the  drum  open  the  key 26 

6.  Method  of  preparing  myogram  for  determination 

of  latent  period.      .        .        ...        .        .        .28 

7.  Apparatus  for  studying  summation  of  contractions.     31 

8.  Scheme  of  electrical  connections  of  primary  coil 

in  two  forms  of  induction  apparatus.  .        .      33 

9.  Relation  of  brain  to  skull  of  frog.  •        •        •     37 

10.  Dissection  of  right  leg  of  frog 38 

11.  Apparatus  recording  beats  of  a  frog's  heart.  .  52 

12.  The  gross  anatomy  of  a  frog's  heart.        •        •        •  53 

13.  Apparatus  to  detect  direction  of  flow  of  current  in 

a   simple  circuit 65 

14.  Apparatus  to  detect  direction  of  flow  of  current 

in  secondary  coil  of  an  induction  apparatus.        .     66 

15.  Diagram  of  location  of  motor  points  on  flexor  side 

of  arm  (after  Erb) 66 

16.  Apparatus     for     unipolar     excitation     of    hvmian 

nerves 67 

17.  Arm  rest  for  support  of  hand  and  electrodes.        .  71 

18.  Apparatus    for    recording   movements    of   thumb.  72 

19.  Apparatus  for  Galvani's  experiment.        .        .        .  yy 

20.  Apparatus  for  observing  polarization  of  electrodes.  81 

21.  Method   of   arranging   non-polarizable   boot   elec- 

trodes in  moist  chamber 83 

22.  Method  of  using  rheocord 87 

23.  Apparatus   for  stimulating  human   nerves  by  the 

direct  current. 91 


XIV  IIvI<USTRATlONS 

24.  Apparatus  for  testing  the  efifect  of  the  direct  cur- 

rent on  the  irritability  of  human  nerves.      .        .     97 

25.  Apparatus  for  recording  reaction  time  to  sound.   113 

26.  Diagram  of  nervous  paths  followed  by  the  nerve 

impulses  causing  the  knee-jerk  and  its  reen- 
forcements 117 

27.  Method  of  supporting  thigh  and  foot,  and  of  re- 

cording the  swing  of  the  lower  leg,  in  the  knee- 
jerk  experiment 118 

28.  Recording  tambour 128 

29.  Sphygmogram  of  a  normal  and  of  a  dicrotic  pulse.   128 

30.  Scheme  of  apparatus  for  studying  the  blood  pres- 

sure of  a  mammal. 135 

31.  Dissection  of  nerves  of  left  side  of  neck  of  rabbit.  139 

32.  Method  of  inserting  cannula  into  carotid  artery.  140 

33.  Tambour  and  neck  spring  used  to  study  the  hu- 

man carotid  pulse. 155 

34.  Method  of  applying  tambour  to  wrist,  to  obtain 

sphygmogram  from  the  radial  artery.        .        -159 

35.  Scheme  of  Jacquet's  sphygmograph.        .        ,        .    163 

36.  Laboratory    form    of    Riva-Rocci    instrument    for 

determining  human  blood  pressure.      .        .        -174 

37.  Diagram  showing  position  of  heart  in  chest,  posi- 

tion of  valves  as  projected  on  wall  of  chest,  and 
the  parts  of  the  chest  where  the  sounds  of  the 
heart  are  heard  best 179 


GENERAL  DIRECTIONS. 

The  laboratory  hours  are  from  one  to  five. 

Each  student  must  have  receipt  from  the  Treasurer,  to 
show  that  the  laboratory  fee  has  been  paid,  and  have  the 
following  articles,  before  beginning  the  work  : 

Towel. 

Strong  scissors  with  fine  points. 
Forceps  with  fine  points. 
Dividers. 

Celuloid  triangle  (6  in.). 
Reading  glass. 
Flesh  pencil. 
Tube  of  office  paste. 

2  sheets  of  millimeter,  cross-section  paper. 
40  sheets  of  note  paper  of  regulation  size. 
40  sheets  of  cardboard  of  regulation  size. 

In  addition,  each  student  must  have  a  copy  of  these  notes, 
and  must  make  a  deposit  of  25  cts.  for  key  of  desk. 

Each  section  will  be  divided  into  two  divisions.  Divis- 
ion A  will  make  the  experiments  in  the  order  in  which  they 
are  given  in  the  notes.  Division  B  will  make  the  experi- 
ments in  the  following  order:  I-VI  inclusive:  XXIV- 
XXXIII,  inclusive,  and  VII-XXIII,  inclusive. 

Two  students  will  work  together.  They  will  be  sup- 
plied with  most  of  the  apparatus  required  in  the  course, 
when  assigned  to  their  desks. 

Each  student  is  expected  to  perform  every  experiment, 
and  to  give  a  full  report  of  the  results,  accompanied  by 
graphic  records  which  he  himself  has  obtained,  when  such 
are  demanded  by  the  experiment.  For  method  of  keeping 
the  notes  and  mounting  the  records  see  Experiment  I. 

Do  not  begin  an  experiuieut  until  yon  have  read  the  di- 
rections in  the  notes,  and  have  clearly  in  mind  the  object  of 
the  experiment. 


XVI 


GENERAL  DIRECTIONS 


Be  prepared  for  a  quiz  on  each  experiment  at  the  time 
it  is  made,  and  to  pass  an  examination  both  on  methods  and 
results  at  the  end  of  the  course. 

Do  not  cut  or  mar  desks  or  stools. 

Learn  to  see  dirt.  Before  leaving  the  laboratory  see 
that  your  table  is  clean  and  neat ;  that  all  apparatus  is  dry ; 
that  the  battery  has  been  disconnected  (it  is  not  enough  to 
leave  the  key  open)  ;  that  all  apparatus  is  covered. 

A  list  of  the  following  apparatus  will  be  found  in  the 
desk,  and  is  to  be  checked  up  in  the  presence  of  the  instruc- 
tor and  signed  by  both  students.  Larger  special  pieces  of 
apparatus  will  be  supplied  from  time  to  time  when  needed. 


Division  A. 


Acetic  acid,   lo  per  cent. 

Battery  jar. 

Board  for  frog. 

Brush  for  salt   solution. 

Bunsen   burner,   with   tubing. 

Two   cells,   dry. 

Clamp,  burette. 

Two    clamps,   cabinet   maker's. 

Clamp,    large   muscle. 

Six  clamps,   for  rods. 

Coil,    aluminum. 

Cloth  to  cover  apparatus. 

Dropper,   coarse   point. 

Electrodes,  boot  form  in  dish. 

Electrodes,   copper. 

Electrode,    indifferent    (sheet    of 

copper). 
Electrode,  active    (brass). 
Electrodes,  pin. 
Electrodes,  platinum. 
Filter  paper. 
Finger  piece,  wooden. 
Fork   and  yoke. 
Glass   Slide  on  support. 
Two   Glasses,   drinking. 
Glass  dish  for  Salt  Solution. 
Hook  for  frog. 
Two  hooks,  pin. 
Induction  Coil. 
Key,   mercury. 
Kymograph  and  drum. 
Lever,  heart,  with  support. 
Lever,    muscle,    heavy. 
Lever,    muscle,    light. 


Ligatures. 

Moist   chamber,  with   wire. 
Two  pads,  gauze. 
Piece  of  metal  to  clamp  to  drum. 
Pins. 

Pinch   cock. 
Plate. 

Potassic  iodide  and  starch  solu- 
tion. 
Pulley. 
Ring  stand. 

Rod,  glass  with  clips   for  boots. 
Rod   to    support   heart   lever. 
Rod,  L,  brass. 
Rod,  Iron. 
Rod,  L,  nickled. 
Rod,  zinc. 

Rubber  band,  large. 
Two    rubber   bands,    thin. 
Two   signals,   electric. 
Spring,  steel  with  pointer. 
Stand,  long. 
Stand,   short. 

Sodium  chloride,  0.6  per  cent. 
Sulphuric  acid,  o.oi   per  cent. 
20  Weights,  ID  grms. 
Silk  thread. 

2   Wires,   insulated,   extra   long. 
2  Wires,   insulated,   long. 
4   Wires,  insulated,  medium. 
2   Wires,   insulated,   short. 
Zinc  Sulphate. 
Two  Zincs  for  Electrodes. 


GENERAL  DIRECTIONS 


XVll 


Division  B. 


Board  for  frog. 

Brush    for   salt   solution. 

Cell,   dry. 

5   Clamps,   for   rod. 

1  Clamp,    cabinet    maker's. 
Cloth   to   cover  apparatus. 
Coil,    aluminum. 
Electrodes,    pin. 

Filter  paper. 
Fork,  with  yoke. 

2  Glasses,  drinking. 
Glass,    for    salt    solution. 
2   Hooks,   pin. 
Induction    coil. 

Key,  inercury. 

Kymograph  with  drum,  4  fans. 

Lever,    muscle,    light. 

Lever,    muscle,    heavy. 

Moist   chamber   with   wire. 

Pins. 


2    Pinch    cocks. 

Plate. 

2    Pneumographs. 

Rod,   nickled. 

2   Rubber  tubes,  with  glass  Ts. 

Signal,  electric. 

Sodium  chloride,  0.6  per  cent. 

Spring,   steel,  with  pointer. 

Stand,  long. 

Stand,   short. 

Tambour,    carotid    with    sprisg. 

Tambour,  radial. 

2   Tambours,   recording. 

20  Weights,   10  grms. 

Wire,   fine   copper. 

2  Wires,   insulated,   extra  long. 

3  Wires,    insulated,    long. 

2    Wires,    insulated,    medium. 
2   Wires,   insulated,   short. 


Students  are  to  use  the  apparatus  supplied  them,  and 
no  other.  In  no  case  is  apparatus  to  be  taken  from  the 
shelves  or  borrowed   from  other  students. 


EXPERIMENT  I. 


p 


Extensibility  and  Elasticity  of  a   Steel  Spring. 

Apparatus. — The  structure  of  the  drum  kymograph, 
the  method  of  fastening  the  paper  on  the  drum,  of  blacken- 
ing the  paper,  and  of  fixing  the  record,  will  be  explained 
by  the  instructor. 

Examine  your  kymograph  with  care  and  be  sure  that 
you  understand  how  the  clockwork  is  wound  up ;  how  to 
change  the  gearing  so  as  to  obtain  the  faster  and  slower 
speeds  of  the  drum ;  how  to  arrange  drum  to  be  driven  by 
the  clockwork  or  to  be  rotated  by  hand ;  and  how  to  raise 
and  lower  the  drum.  The  instrument  will  be  in  order  when 
you  receive  it  and  must  be  in  order  when  you  return  it. 

Mount  spring  and  heavier  mus- 
cle lever  on  the  longer  iron  stand. 
0  i       ir  ^^  shown  in  diagram.     The  stand 

fC^IJill^  holding  the  recording  instruments 

should  always  be  placed  to  the 
right  of  the  kymograph,  so  that 
these  instruments  shall  point  in 
the  direction  that  the  drum  re- 
volves. The  clockwork  turns 
the  drum  clockwise,  and  when 
it  is  turned  by  hand  it  should 
be  rotated  always  in  this  direc- 
tion. If  the  drum  be  rotated 
backward,  the  recording  points 
are  liable  to  be  injured.  All 
records  should  read  from  left  to  right.  Decide  at  what 
part  of  the  drum  the  record  is  to  be  made  before  finally 
clamping  the  recording  apparatus  on  the  stand.  Fasten 
two  pieces  of  thread  to  the  writing  lever  at  the  hole  second 
from  the  axis,  and  attach  one  of  the  threads  to  the  spring 


rD 


Apparatus  for  re- 
cording extensibility  and  elas- 
ticity of  a  steel  spring.  A, 
joint  of  paper  on  drum;  B, 
lever;  C,  supporting  screw;  D, 
pin  hook  for  weight;  E,  steel 
spring;  F,  V,  clamps. 


2  EXPERIMENT  I. 

8  cm.   from  brass   supporting'  rod.  and  the  other  to  a  pin 
hook  as  shown  in  diagram.    Observe  the  following  cautions: 

I. — See  that  the  axis  of  the  writing  lever  is  horizontal. 
2. — See  that  the  thread  connecting  the  lever  with  the 
spring  is  vertical. 

3. — See  that  the  knots  are  securely  fastened. 

4. — See  that  every  clamp  is  screwed  firmly  in  place. 

Now  remove  the  drum  from  the  k}mograph,  fasten  a 
sheet  of  glazed  "curve  paper"  smoothly  aroinid  the  drum, 
and  blacken  the  surface  evenly  over  the  gas  flame,  rotating 
the  drum  constantly  so  as  not  to  burn  the  paper.  Replace 
the  drum,  place  the  kymograph  so  that  the  writing  lever 
is  tangent  to  drum  surface,  touching  lightly.  Notice  that 
lever  writes  an  arc  on  a  curved  surface.  If  barely  touching 
when  horizontal,  it  will  leave  the  surface  and  fail  to  vv'rite 
as  it  moves  up  or  down.  The  lever  should  press  on  the 
drum  just  enough  to  write  for  2  or  3  cm.  above  and  below 
the  horizontal  line  falling  through  its  axis.  The  position 
of  the  point  with  reference  to  drum  and  joint  of  paper  is 
indicated  in  the  diagram. 

Experiment. — Turn  the  drum  by  hand  in  a  clockwise 
ilirection  to  draw  a  base  line  3  or  4  inches  long.  Turn  it 
Lack  (taking  care  not  to  injure  writing  points)  to  the  smart- 
ing point  and  mark  the  place  by  touching  the  lever  lightly. 
Now  turn  drum  clockwise  3^  cm.  and  then  carefully  place 
a  10  gram  weight  on  the  pin  hook.  Turn  same  distance 
again  and  add  another  weight.  Continue  in  this  manner 
until  9  weights  have  been  added,  then  turn  the  drum  Vi  cm. 
once  more.  The  writing  point  has  now  recorded  the  curve 
of  extensibility  of  the  spring.  To  obtain  curve  of  elasticity, 
turn  drum  3/2  cm.  in  same  direction  and  remove  one  weight, 
and  continue  in  this  manner  until  all  the  weights  are  ofif, 
then  turn  Yi  cm.  once  more,  and  mark  point  by  touching 
lever. 

The  vertical  lines  on  the  drum  should  be  of  equal  length. 
If  they  are  not,  try  to  account  for  the  error.  Since  steel  is 
])erfectly  elastic,  the  writing  point  should  return  to  the  base 
line.     Tf  it  does  not.  trv  to  account  for  the  difference. 


KLASTICrTV  OF  STEEI.   SPRING. 


MOUNT  !XG  OF   CL'RVES. 


With  triangle  and  a  needle,  or  other  instrument  with  a 
sharp  point,  draw  a  rectangle  about  each  record  worih 
preservation.  It  is  desirable  to  leave  a  generous  margin 
about  the  curve.  Cut  out  piece  thus  outlined,  and  mount 
on  the  cardboard  by  glueing  the  corners  on  with  a  little 
paste.  If  a  knife  be  used  to  cut  off  the  piece,  cut  upon  a 
piece  of  cardboard.  Do  not  cut  on  the  table.  To  protect 
the  curves,  place  over  them  the  sheet  of  paper  upon  which 
the  notes  concerning  the  experiment  have  been  written. 
TvCt  the  right  hand  end  of  the  sheet  overlap  the  cardboard 
slightl}\  and  fasten  it  to  the  back  of  the  cardboard  with 
paste. 

THE   student's   notes. 

Write  as  plainly  as  possible  on  the  upper  left  hand  corner 
of  the  paper  which  covers  the  curves,  your  name  and  the 
number  of  each  of  the  experiments  mounted  on  the  card. 
Also  head  each  mounted  curve  with  the  number  of  the 
experiment  and  the  letter  of  the  subheading  to  which  it 
belongs,  and  label  the  corresponding  notes  on  the  cover 
paper  in  like  manner. 

The  notes  should  contain  an  accurate  statement,  not  of 
what  the  books  say  on  the  subject,  but  of  the  results  act- 
ually obtained  by  you  in  performing  the  experiment.  Do 
not  describe  the  method  of  the  experiment  unless  it  is 
different  from  the  directions  in  these  notes,  in  wdiich  case 
let  the  explanation  contain  all  the  facts  required  to  let 
another  understand  the  exact  conditions  of  the  work.  Men- 
tion all  sources  of  error  which  are  likely  to  arise  from  the 
method  used.  This  is  most  important.  An  apparatus  is 
a  servant  employed  to  make  observations.  You  must  know 
in  what  respects  its  report  is  to  be  trusted  and  where  it  is 
liable  to  deceive.  It  is  worse  than  useless  to  employ  appar- 
atus in  experiments  or  in  physical  examinations  unless  you 
know  your  apparatus  thoroughly.  If  the  results  obtained 
differ  from  those  which  you  know  to  be  usually  obtained  in 
similar   cases,    try    to    explain    why    the    dift"erence    occurs. 


4  EXPERIMENT  I. 

Look  Upon  each  experiment  as  a  piece  of  original  research, 
and  do  not  be  satisfied  with  simply  carrying  out  directions. 
Learn  to  cultivate  the  power  of  independent  observation 
and  thought.  You  will  be  judged  as  much  by  the  original- 
ity displayed  in  your  reports  as  by  the  accuracy  of  your 
work.  If  you  can  learn  to  observe  accurately  and  to  record 
your  observations  concisely  and  at  the  same  time  in  suffi- 
cient detail  to  make  another  understand  the  results  of  your 
experiments,  you  will  be  able  to  make  a  valuable  physical 
examination  and  keep  a  reliable  case  book. 


FJ,ASTIC1TY  OF   STEEL  SPRING. 


EXPERIMENT  r. 


ICLASTICITY  OF  FROG  S  MUSCLE). 


EXPERIMENT  II. 


Extensibility   and   Elasticity   of  Frog's  Muscle. 

Apparatus. — Mount  moist  chamber  on  standard,  and 
fasten  threads  to  lever  so  that  it  will  magnify  the  movement 
6  times.  Have  all  apparatus  in  readiness  and  the  drum 
blackened  before  preparing  the  muscle. 

MUSCLE  PREPARATION. 

Kill  a  frog  under  the  direction  of  a  demonstrator. 
Straighten  hind  legs  by  letting  hand  glide  over  body,  and 

wrap  legs  in  dry  cloth.  Insert 
one  blade  of  strong  scissors  into 
mouth  as  far  back  as  angles  of 
jaw,  and  with  the  other  blade 
across  the  head  as  far  back  as 
possible,  remove  skull  by  a  single 
cut  of  the  scissors.  In  making  the 
cut,  hold  frog,  head  down,  over 
a  plate.  Cut  off  hind  legs  close 
to  body.  As  there  is  a  possibil- 
ity that  the  brain  may  recover 
from  the  shock,  complete  its 
destruction  by  thrusting  a  blade 
of  the  scissors  into  the  cranial 
cavity  and  breaking  up  the  brain.  There  is  no  evidence 
that  the  rest  of  the  nervous  system  is  capable  of  feeling; 
nevertheless,  as  a  matter  of  precaution,  destroy  the  spinal 
cord  and  all  remnants  of  the  brain  with  a  pithing  needle. 
Be  sure  that  all  of  the  central  nervous  system  has  been 
destroyed,  for  even  comparatively  small  parts  in  cold- 
blooded animals  can  recover  from  severe  shock. 

Remove  the  skin  from  the  leg,  and  see  that  it  does  not 
touch  the  muscles,  as  there  is  a  secretion  upon  the  skin 
which  is  injurious.  Now  put  leg  on  piece  of  filter  paper 
moistened  with  physiological  salt  solution.     Clean  off  the 


/ 

P        \ 

A 

d 

= 

a3te 

p 

n 

1 

1                  ^ 

\ 

Fig.  2.  Apparatus  for  record- 
ing extensibility  and  elasticity 
of  frog's  muscle.  A,  moist 
chamber;  B,  femur  fastened  in 
bone  clamp;  C,  muscle. 


8  EXPERIMENT   11. 

thigh  muscles  from  femur  without  injuring  tendon  of  the 
gastrocnemius  muscle.  Cut  tendo-Achillis  below  ankle  and 
separate  gastrocnemius  from  tibia.  Remember  that  you  are 
not  in  the  dissecting  room,  and  that  you  are  dealing  with 
living  tissues.  Do  not  touch  the  muscle  with  the  fingers, 
nor  pinch  it.  nor  injure  it  by  pulling  on  it,  etc.  It  can  be 
handled  by  holding  the  tendon  with  forceps.  Cut  off  tibia 
just  below  knee,  insert  and  fasten  femur  in  clamp  in  moist 
chamber,  put  pin  hook  through  middle  of  tendo-Achillis, 
and  in  doing  this  avoid  pulling  on  muscle.  Place  a  piece 
of  wet  filter  paper  in  the  moist  chamber. 

a.  Experiment. — Repeat  the  work  of  Experiment  i, 
allowing  an  interval  of  ten  seconds  between  the  addition 
or  removal  of  any  two  weights.  The  drum  should  be  moved 
at  the  end  of  the  lo  seconds,  in  order  that  any  delayed  effect 
of  the  change  in  load  may  be  recorded  in  the  proper  place. 
After  removing  last  weight  and  waiting  to  seconds,  if  the 
writing  point  has  not  returned  to  the  base  line,  turn  drum 
again  and  wait  one  minute ;  repeat  this,  turning  drum  at 
intervals  of  one  minute,  until  lever  ceases  to  rise  or  base 
line  is  reached.  Plot  the  curves  of  extensibility  and  elas- 
ticity of  muscle.  If  several  curves  are  taken  with  the  same 
muscle,  keep  them  all  and  label  t.  2,  3,  etc.  Explain  in 
your  notes  the  differences  observed. 

b.  Pi,oTTiNG  OF  Curves. — The  curves  drawn  by  the 
writing  point  are  inexact  in  two  respects :  the  point  does  not 
move  in  a  vertical  line,  and  the  drum  may  not  be  moved 
equal  distances.  To  obtain  exact  curves  of  the  extensibility 
and  elasticity,  proceed  as  follows.  Take  a  piece  of  cross  sec- 
tion paper  and  draw  heavy  lines  for  the  two  axes.  Mark  dots 
at  equal  distances  along  the  horizontal  axis  (the  abscissa) 
and  number  them  0-10-20,  etc.,  to  represent  the  weights 
used.  Place  along  the  vertical  axis  (the  ordinate)  at  equal 
distances  the  numbers  0-5-10-20,  etc.,  to  represent  the  num- 
ber of  millimeters  through  which  the  writing  point  moved. 
As  the  separate  movements  are  small,  it  may  be  wise  to 
let  each  millimeter  of  movement  be  represented  by  2  or  5 
millimeters  of  the  paper.  Measure  with  the  aid  of  a 
magnifying  glass  the  exact  height  of  each  movement  record- 


ELASTICITY  OF  FROG  S  MUSCLE.  9 

£d.  It  is  usually  best  to  make  the  measurements  all  from  the 
base  line.  The  amount  of  the  individual  movements  can 
be  obtained  by  subtraction.  Give  these  measurements  in 
your  notes,  in  order  that  they  may  be  checked,  and  enter 
the  results  on  the  chart,  by  marking,  for  each  observation, 
a  dot  at  the  point  of  intersection  of  the  vertical  line  corres- 
ponding to  the  weight,  and  the  horizontal  line  corresponding 
to  the  height  of  lift.  Now  connect  the  dots  by  straight 
lines.  Mount  the  plotted  curve  at  the  side  of  the  original. 
How  does  extensibility  differ  from  elasticity?  How  do  the 
curves  obtained  from  muscle  differ  from  those  obtained 
from  a  steel  spring?  How  do  the  different  curves  of  elas- 
ticity obtained  from  the  same  muscle  differ?     Explain. 


ro  EXPERIMENT    II. 


KI.ASTlCiTY  OI"   F'KCH-;.  S   fJlISCLP;. 


EXPERIMENT    II. 


RESPONSE  OF  MUSCI.E  TO  INDUCTION   SHOCKS. 


13 


EXPERIMENT  III. 

Response  of  Muscle  to  Making  and  Breaking  Induction 

Shocks  of  Various  Strengths,  and  Use  of 

Short  Circuit  Key. 

Apparatus. — Before  preparing  the  muscle,  arrange 
apparatus  as  indicated  in  the  diagram,  mounting  the  moist 
chamber  and  lever  on  the  tall  stand.  Employ  the  light 
muscle  lever  in  this  experiment.  When  the  weight  is  sup- 
ported so  as  not  to  bring  a  strain  on  the  muscle  until  it 


^^^ 


Pig-.  3.  Apparatus  for  recording  contractions  of  frog's  muscle,  excited  by  in- 
duction shocks.  A,  pin  electrode;  B,  primary  coil;  C,  C,  posts  i  and  2;  D,  dry 
cell;  B,  mercury  key;  F,  secondary  coil;  G,  short-circuiting  key;  H,  light 
muscle  lever;  I,  yoke  of  lever  arranged  to  support  it;  J,  scheme  of  mercury  key 
in  primary  circuit. 

contracts,  we  have  what  is  known  as  an  "after-loaded  con- 
traction." In  this  case  the  muscle  is  to  be  after-loaded. 
Connect  the  muscle  with  the  sixth  hole  of  the  lever ;  see 
that  the  thread  is  vertical ;  rotate  the  yoke  carrying  the  axis 
of  the  lever,  until  it  supports  the  lever  when  the  thread  is 
tense,  and  tighten  the  screw  that  fastens  the  yoke  to  the 
rod.  Now  suspend  ten  grams  from  the  lever.  To  obtain 
good  results  it  is  necessary  to  observe  the  following  direc- 
tions : 


14  EXPERIMENT  III. 

I. — Clamp  mercury  key  to  edge  of  table. 

2. — Clean  and  brighten  all  wires  at  points  of  metallic 
contact. 

3. — Connect  wires  of  battery  circuit  (the  primary  cir- 
cuit) to  posts  I  and  2  of  induction  apparatus. 

4. — Turn  binding  screws  firmly  down. 

5. — Leave  key  in  battery  circuit  open  when  not  in  use, 
to  prevent  waste  of  battery. 

6. — See  that  surface  of  mercury  in  key  is  bright,  and 
that. platinum  loop  touches  mercury  in  both  cups  when  key 
is  closed. 

7. — Avoid  closing  key  so  forcibly  as  to  jar  mercury 
globules. 

8. — See  that  thread  is  tense  when  lever  is  properly  sup- 
ported. 

9. — When  it  is  not  the  intention  to  stimulate  the  muscle, 
see  that  short-circuiting  key  is  closed,  to  guard  muscle 
against  accidental  closures  of  primary  circuit. 

Some  facts  Regarding  Iiidiictioji  Apparatus. 

Recall  the  following  facts  concerning  the  induction 
apparatus.  The  wire  of  the  primary  coil,  through  which 
the  battery  current  flows,  has  no  metallic  connection  with 
the  ware  of  the  secondary  coil,  and  consequently  the  battery 
current  does  not  enter  the  secondary  coil.  The  current 
which  is  used  to  excite  the  muscle  is  an  induced  current  of 
very  brief  duration,  which  develops  in  the  secondary  coil 
at  the  instant  that  the  battery  current  is  thrown  into,  or  is 
withdrawn  from  the  primary  coil.  It  is  the  disturbance  of 
the  magnetic  field  about  the  primary  coil,  that  causes  the 
induced  currents  in  the  secondary,  and  the  induced  currents 
are  of  very  brief  duration,  lasting  only  until  equilibrium 
has  been  established.  The  nearer  the  secondary  approaches 
the  primary  coil,  the  more  it  comes  under  the  influence  of 
the  magnetic  field  about  it,  and  the  stronger  the  induced  cur- 
rents become.  Like  movements  of  the  secondary  coil,  result 
in  a  more  and  more  rapid  growth  in  the  intensity  of  the  in- 
duced currents  as  the  primary  coil  is  approached  ;  a  move- 
ment of  a  millimeter  when  the  secondary  is  close  to  the  pri- 


RESPONSE  OF  MUSCLE  TO   INDUCTION   SHOCKS.  15 

mary  increases  the  induced  current  as  much  as  a  movement 
of  a  centimeter  or  more  when  the  coils  are  far  apart.  Rota- 
tion of  the  secondary  coil  on  the  pivot,  because  changing  the 
angle  at  which  the  lines  of  magnetic  force  will  cut  the  wind- 
ings, also  influences  the  development  of  the  induced  cur- 
rents, and  they  become  less  the  more  the  angle  between  the 
tv/o  coils  approaches  a  right  angle. 

Why  is  the  making,  weaker  than  the  breaking  induction 
shock  ?  When  the  battery  current  is  made,  an  electro- 
motive force  is  set  up  in  the  primary  coil,  and  this  force 
induces  a  counter  electro-motive  force  in  that  coil  of  opposite 
direction  to  that  of  the  battery  current.  As  a  result,  the 
disturbance  in  the  magnetic  field  about  the  primary  coil  is 
slow  to  develop  and  comparatively  slight,  and  the  making 
induced  current  in  the  secondary  coil  gains  its  full  intensity 
slowly  and  is  feeble.  When  the  battery  current  is  broken, 
the  electro-motive  force  induced  in  the  primary  coil  has  the 
same  direction  as  that  of  the  battery  current,  and  conse- 
quently the  breaking  induced  current  in  the  secondary  coil 
gains  its  full  intensity  very  rapidly  and  is  very  strong. 

a.     Response  to  Making  and  Breaking  Shocks  of  Increas- 
ing Strength. 

Experiment. — Place  muscle  preparation  in  the  moist 
chamber,  insert  pin  electrode  into  the  tendo-Achillis  (not 
the  muscle  substance).  Connect  the  short  wire  fastened 
to  a  bit  of  nickled  rod,  with  binding  post  on  support 
which  carries  the  muscle  clamp.  The  exciting  current 
will  pass  through  muscle  from  end  to  end.  Place 
kymograph  so  that  lever  bears  lightly  on  drum  near 
the  joint  of  the  paper.  Move  secondary  coil  as  far  from 
primary  as  the  construction  of  instrument  permits,  then 
turn  it  on  the  pivot  until  it  is  at  right  angles  to  the  primary 
coil.  Now  open  short  circuit  key  and  make  and  break  the 
primary  circuit  by  means  of  the  mercury  key :  no  contrac- 
tion. The  simulus  is  sub-minimal.  Gradually  turn  the 
coil  to  strengthen  the  induced  current,  making  and  breaking 
the  circuit  at  each  new  position  of  coil.  A  position  will  be 
found,  either  while  turning  the  coil  or  afterwards  by  sliding 
3 


1 6  EXPERIMENT   III. 

it  towards  the  primary,  at  which  a  small  contraction  will 
result.  Notice  that  the  contraction  occurs  on  breaking  the 
circuit  and  that  no  corresponding  making  contraction  is 
seen.  Now  give  muscle  a  rest  of  3^  a  minute  and  then 
try  to  put  the  secondary  coil  in  such  a  position  that  the 
contraction  will  be  so  small  as  to  be  scarcely  visible.  Such 
a  contrac:ion  is  said  to  be  minimal.  These  later  trials  should 
be  made  at  intervals  of  not  less  than  lo  seconds.  Now  move 
the  drum  a  few  centimeters,  and  record  first  a  minimal  con- 
traction, and  then,  i  cm.  apart,  a  series  of  breaking  con- 
tractions obtained  by  stimulating  with  gradually  increasing 
stimuli.  In  stimulating,  make  the  circuit,  wait  5  seconds, 
then  break,  and  wait  10  seconds.  Soon  a  contraction  will 
appear  when  the  circuit  is  made,  but  smaller  than  the  break- 
ing contraction  that  goes  with  it.  If  the  secondary  coil  has 
not  been  moved  too  rapidly  this  first  making  contraction 
will  be  nearly  minimal.  After  a  minimal  making  contraction 
has  been  obtained,  continue  stimulating  and  recording  as 
before,  excepting  that  now  drum  is  to  be  turned  ^  cm. 
after  each  contraction.  After  a  time  the  breaking  and  mak- 
ing contractions  will  be  maximal,  i.  e.,  will  cease  to  grow 
with  increasing  strength  of  current,  and  if  the  work  is 
continued,  a  second  growth  in  height  of  contractions  may 
be  seen,  and  supra-maximal  contractions  be  recorded.  Mark 
on  the  record  to  indicate  which  contraction  is  a  minimal 
break,  a  minimal  luake,  a  maximal  break  and  a  maximal 
make. 

b.     Use  of  Short  Circuit  Key. 

Move  drum  away,  then  slide  secondary  coil  to  a  posi- 
tion which  excites  making  contractions  about  half  as  high 
as  the  corresponding  breaks.  Return  drum  and  record  four 
making  and  four  breaking  contractions,  stimulating  with 
same  time  intervals  as  in  part  a,  but  with  the  strength  of 
current  unchanged.  Close  the  short  circuit  key  and  stimu- 
late :  no  contraction.  Two  paths  are  now  open  to  the  cur- 
rent, and  the  current  is  divided  between  them  in  inverse 
proportion  to  the  resistances.  The  muscle,  having  much 
Sfreater    resistance    than    the    metal    of    the    short    circuit 


KKSPONSE  OF  MUSCLE  TO   IXDLXTIOX   SHOCKS.  1 7 

key,  gets  so  little  current  that  the  stimulus  is  sub-minimal. 
This  method  of  dividing  the  current  is  techincally  known 
as  "shunting." 

Leaving  coil  in  same  position,  record  a  series  of  four 
making  contractions,  cutting  out  breaks  with  short  circuit 
key,  then  record  a  series  of  four  breaks,  cutting  out  the 
makes  in  the  same  manner.  Indicate  which  are  makes  and 
which  are  breaks  in  the  last  group  of  records. 


:xi'r;RiMF.N"i'  J 1 1. 


RESPONSE  OF  MUSCLE  TO  INDUCTION   SHOCKS.  I  9 


KXPEKIAII' NT    111 


CUR\E   OF    WORK.  ,     ,  .     .  21 


EXPERIMENT  IV. 

Relation   of  Amount    of    Load    to    Height  of  Lift  and 
Quantity  of  Work  Done. 

Apparatus. — The  same  apparatus  is  to  be  employed  as 
in  Experiment  3,  except  that  the  heavy  muscle  lever  is  to 
be  used.  Because  of  the  heavy  load  to  be  carried,  care 
must  be  taken  to  fasten  securely  all  clamps,  threads,  and 
hooks.  The  muscle  is  to  be  after-loaded,  and  the  support- 
ing screw  must  be  carefully  adjusted  so  that  the  whole 
height  of  each  contraction  shall  be  recorded.  Have  20  ten- 
gram  weights  ready  for  use. 

a.  Experiment. — Place  muscle  in  moist  chamber,  and 
make  electrical  connections  as  in  Experment  3.  Find 
strength  of  current  required  to  produce  maximal  breaking 

contractions  of  unloaded  mus- 
cle. In  doing  this  avoid  fa- 
tiguing muscle  by  too  frequent 
excitations.  For  stimuli  use 
maximal  breaks  at  intervals  of 
15  seconds,  and  cut  out  the 
makes  with  short-circuiting 
key.  Record  on  the  drum  at 
distances  of  ^  cm.,  the  con- 
tractions obtained  with  o,  10, 
20,  30,  etc.  grams,  and  contin- 
ue the  addition  of  weights  un- 

Fig.  4.   Curveofliftandofwork.        ^{\     ^\jq     muSClc     CaU     UO     lougcr 
A,  curve  of  hit;    B,  curve  of  work.  " 

lift  the  load.  If  more  than  one 
experiment  is  made  with  the  same  muscle,  state  the  fact, 
since  fatigue  will  modify  the  results. 

b.  Plotting  of  Curves. — State  in  tabular  form  on  the 
cardboard,  by  the  side  of  the  original  curve,  the  recorded 
height  of  lift,  and  the  actual  work  done  by  each  of  the  con- 
tractions, (the  work  being  th*e  product  of  the  height  times 
the  weight  lifted). 


30 

V 

so 

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A 

10 

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0 

\ 

/grms 

sw> 

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lOV 

\ 

y 

6v(/ 

B 

22  EXPERIMENT   IV. 

To  plot  the  curves  of  lift  and  work,  take  a  piece  of  cross- 
section  paper,  about  lo  cm.  square,  and  lay  off  axes  as 
shown  in  diagram.  Plot  above  the  abscissa  line  a  curve 
showing  the  heights  of  the  contractions, — the  ordinates  rep- 
resenting" the  distances  through  which  the  weight  was  moved 
and  the  abscissas  the  weights.  Plot  below  the  abscissa  line 
the  curve  of  work,  the  ordinates  representing  the  work  and 
the  abscissas  the  weights.  In  plotting  the  curves,  i  mm.  of 
cross  section  paper  can  be  used  to  represent  any  desired 
value  of  the  curve  to  be  plotted.  The  curve  can  magnify 
or  reduce  the  values  actually  obtained.  For  example,  i;  2, 
or  3  mm.  on  the  cross-section  paper  can  stand  for  i  mm.  of 
lift,  and  5,  10  or  20  mm.  on  the  paper  can  represent  100 
grammillimeters.  Be  sure  to  state  on  the  plotted  curve  the 
values  of  ordinates  and  abscissas. 

With  what  weight  was  the  greatest  amount  of  work 
done?  What  was  the  actual  amount  of  work  done  with 
this  weight?     Have  the  results  any  practical  bearing? 


curve;  of  work.  23 


24  EXrURIMRNT   IV. 


TIME  RELATIONS   OF   MYOGRAM.  25 


EXPERIMENT  V. 

Time  Relations  of  Myogram. 

The  record  of  a  single  muscle  contraction  is  called  a 
myogram.  Hitherto  we  have  been  concerned  onl}'  with 
the  height  of  the  myogram,  which  can  be  best  observed 
when  recorded  on  a  stationary-  drum.  In  order  to  study  the 
time  relations  of  the  myogram,  the  record  will  have  to  be 
taken  on  a  moving  drum,  and  the  rate  of  movement  of  the 
drum  be  determined  with  a  tuning  fork. 

a.     Influence  of  Rate  of  Dniiii  on  form  of  Myogram. 

There  are  toda}^  a  great  variety  of  methods  for 
obtaining  graphic  records  of  physiological  processes  and 
the  changes  which  they  undergo  under  normal  and  patho- 
logical conditions.  In  many  cases  these  records  are  taken 
on  moving  surfaces,  and  it  is  important  that  one  should  be 
able  to  estimate  the  influence  of  the  rate  of  motion  of  the 
surface  on  the  shape  of  the  curve. 

Apparatus. — The  apparatus  for  supporting  the  muscle 
and  recording  its  contraction,  and  the  electrical  connections 
with  the  induction  coil  are  to  be  the  same  in  this,  as  in 
Experiment  3,  the  lighter  muscle  lever  being  used.  In  this 
experiment,  however,  the  key  in  the  primary  circuit,  instead 
of  being  opened  by  hand,  is  to  be  opened  automatically  by 
the  drum  when  it  is  revolved.  That  this  may  be  done, 
fasten  a  frog  board  by  its  iron  rod  to  clamp  on  short  stand. 
Place  key  in  primary  circuit  on  the  board,  so  that  it  projects 
for  two-thirds  of  its  length  bcA'ond  it,  and  clamp  key  to 
board  by  a  cabinetmaker's  clamp.  Adjust  board  so  that 
top  of  key  is  just  above  the  level  of  the  top  of  the  drum. 
Clamp  to  the  top  of  the  drum,  so  that  it  projects  a  couple 
of  cm.  beyond  it,  the  piece  of  metal  supplied  for  this  pur- 
pose. See  that  the  piece  of  metal  does  not  change  its  place, 
as  it  must  hold  a  constant  position  with  respect  to  the  sur- 
face of  the  drum.  Now  move  the  key  just  near  enough  to 
enable  the  projecting  piece  of  metal  to  open  it. 


26 


KXPF.RIMENT   V. 


net  maker's  clamp;  C,  mercury  key; 
D,  handle  of  key;  E,  piece  of  metal; 
F,  wires  to  primary  circuit;  G.  tuning 
fork;  H,  yoke. 


Experiment.  —  Blacken  a 
drum  ;  bring  key  into  position 
to  be  opened  when  drum  is 
turned ;  leave  key  open  when 
the   current    is    not    wanted. 

Prepare  a  gastrocnemius 
muscle ;  suspend  it  in  moist 
chamber  and  connect  it  with 
lever ;  thrust  pin  of  pin  elec- 
trode through  tendon  ;  adjust 
support  so  that  muscle  shall 
Fig.  5.   Apparatus  for  automatically  be   aftcr-loadcd   zvJicii    thread 

exciting  muscle  by  letting  the  drum      •       .  j    ±1        1  •       1 

open  the  key.     A,  frog  boird;  B,  cabi-     W    tCllSC    mid    tllC    leVCl'    IS    llOK- 

izontal.  Let  short-circuiting 
key  be  closed  when  it  is  not 
desired  to  excite  muscle ; 
place  secondary  coil  so  that  muscle  shall  give  a  maximal 
breaking  contraction ;  short  circuit  all  making  shocks ; 
rotate  drum  so  that  the  part  which  opens  key  will  point 
away  from  it.  Now  place  stand  so  that  the  lever  will  write 
well  upon  the  drum.  Close  key  in  primary  circuit  and  then 
open  short-circuiting  key.  Now  open  key  in  primary  circuit 
by  rotating  drum  by  hand  very  slowly.  A  breaking  con- 
traction will  be  recorded.  Do  not  move  the  kymograph,  or 
the  stands  holding  key  and  lever.  Repeat  the  experiment 
four  times,  each  time  rotating  the  drum  somewhat  faster. 
Fix  the  record.  State  in  notes  in  what  respects  the  myo- 
grams obtained  differ.  Save  the  muscle  to  test  the  appar- 
atus in  part  h. 

b.     Time  Relations  of  Myogram. 

Apparatus. — Use  the  same  apparatus  as  in  a,  with  the 
following  additions :  Mount  on  long  stand  beneath  the 
muscle  lever  a  tuning  fork,  to  mark  rate  of  movement  of 
drum.  Put  on  the  wire  spring,  used  in  Experiment  I,  a 
celluloid  pointer,  and  clamp  the  spring  beneath  the  fork,  to 
give  a  base  line  to  be  used  in  measuring  the  curves.  See 
that  the  three  writing  points  are  in  the  same  vertical  line. 

Experiment. — The  latent  period,  the  duration  of  the 
])eri()d  of  rise  and  of  the  ])eriod  of  fall,  are  all  longer  for 


TIME   RELATIONS   OF    MYOGRAM.  27 

a  fatigued  than  for  a  fresh  muscle;  it  is  therefore  best  to 
test  apparatus  with  muscle  used  in  part  a.  When  you  have 
learned  to  perform  the  experiment  promptly  prepare  a  fresh 
muscle.  Ascertain  the  current  just  strong  enough  to  give 
a  maximal  breaking  contraction,  and  in  doing  this  avoid 
exciting  the  muscle  more  often  than  once  in  ten  seconds, 
and  call  out  as  few  contractions  as  possible.  If  you  have 
to  repeat  the  experiment  frequently,  state  the  number  of 
the  contraction  the  curve  of  which  is  measured.  After  the 
drum  has  been  blackened,  and  the  mercury  key  has  been 
placed  so  that  it  will  be  opened  when  the  drum  revolves, 
see  that  the  lever  is  horizontal  when  resting  on  its  support 
with  thread  tense.  Then  move  long  stand  so  that  fork  and 
muscle  lever  will  write  on  drum.  If  now  the  drum  is 
revolved,  the  mercury  key  will  be  opened  when  the  muscle 
lever  is  at  a  certain  point  on  the  drum  surface.  To  find 
what  this  point  is,  with  short  circuit  key  closed,  close  mer- 
cury key ;  then  open  short  circuit  key,  and  open  mercury 
key  by  revolving  the  drum  z'ery  slozuly.  The  recorded  myo- 
gram should  be  almost  a  single  line.  The  contraction 
of  the  muscle  will  mark  the  point  of  drum  which  was  oppos- 
ite the  end  of  the  lever  when  the  muscle  was  stimulated. 
Now,  without  changing  position  of  key,  drum,  or  lever, 
close  short  circuit  key,  revolve  drum  two-thirds  the  way 
round,  put  yoke  on  fork,  close  mercury  key  ;  then  pull  yoke 
ofif  of  fork  and  immediately  open  mercury  key  by  revolving 
drum  rapidly.  Stop  drum  at  the  close  of  one  revolu'don. 
If  the  muscle  had  contracted  immediately  the  second  curve 
would  have  begun  to  rise  at  the  same  point  as  the  first. 
It  does  not,  because  the  muscle  has  a  latent  period.  The 
distance  between  the  beginning  of  the  two  curves  shows 
the  length  of  this  period,  because  the  tuning  fork  curve 
enables  us  to  know  how  long  the  drum  took  to  traverse  this 
distance. 

c.     Measurement    of    Records    and    Coiupntation  of  Time 
Interz'als. 

To  determine  the  latent  period,  it  is  first  necessary 
to  fix  the  exact  points  at  which  the  two  contractions 
began.     Draw  through    the    point    of    origin    of    the    first 


28 


EXPERIMENT   V. 


recorded  contraction  the  line  MN,  perpendicular  to  the 
base  line.  To  fix  the  point  at  which  the  second  contraction 
began,  draw  on  the  curve  two  fine  parallel  lines,  one  just 
above  and  one  just  below  the  line  traced  by  the  lever,  as 
at  AB,  to  aid  the  eye  in  fixing  the  point.  Draw  through  it 
the  line  OP  and  estimate  MO,  the  latent  period,  in  thou- 
sandths of  a  second.  One  double  vibration  of  the  fork  is 
ten  thousandths  of  a  second.  A  good  way  of  ascertaining 
the  length  of  the  latent  period,  is  to  estimate  the  value  of 
one  millimeter  of  drum  surface  in  thousandths  of  a  second, 
by  dividing  the  time  of  one  double  vibration  of  the   fork 


Fig.  6.     Method  of  preparing  myogram  for  de- 
termination of  latent  period. 

by  the  number  of  millimeters  in  the  wave  which  is  recorded 
most  nearly  between  MO,  and  multiplying  this  value  by  t4^ 
number  of  millimeters  in  the  recorded  latent  period. 

To  detenPiine  the  period  of  contraction,  draw  TQ  per- 
pendicular to  MN  and  tangent  to  the  muscle  curve  at  Q. 
With  a  radius  equal  to  the  length  of  the  writing  lever  and 
a  center  on  the  base  line  traced  by  the  muscle  lever,  as  at 
R,  revolve  Q  to  this  base  line  at  S.  draw  the  perpendicular 
UV  through  S,  and  estimate  the  number  of  thousandths 
of  a  second  between  OU.  To  do  this  count  the  complete 
waves,  and  estimate  in  tenths  the  fractions  of  waves.  The 
line  UV  must  not  be  drawn  through  Q,  because  the  distance 
WQ  is  due  to  the  fact  that  the  muscle  lever  draws  an  arc 
instead  of  a  straight  line.  To  determine  the  period  of  relax- 
ation, draw  XY  through  the  point  where  the  muscle  curve 
strikes  the  base  line  at  X. 

State  in  notes  length  of  latent  period,  contraction  period, 
and  relaxation  period,  in  tabular  form.  Also  mention  the 
most  likelv  sources  of  error. 


TIME   RELATIONS   OE    MYOGRAM.  29 


30 


kxpkkimknt  v. 


CKNESIS  01'  TJCTANUS. 


31 


EXPERIMENT  VI. 


Fig.  7.  Apparatus  for  studying  sum- 
mation of  contractions.  A,  block  of 
wood  wound  with  aluminum  wire; 
B,  primary  coil;  C,  C,  posts  i  and  2; 
U,  dry  cell;  E,  bare  end  of  insolated 
wire  turned  back  on  itself. 


Genesis  of  Tetanus. 

Apparatus. — The  apparatus  is  to  be  arranged  as  in 
Experiment  3,  except  that  the  mercury  key  is  to  be  omitted, 
and  the  current  of  the  battery  circuit  is  to  be  made  and 
broken  as  follows. 

Fasten  the  block  of  wood 
on  which  the  aluminum 
wire  is  wound,  to  the  edge 
of  the  table  by  a  cabinet 
maker's  clamp.  Connect  the 
binding  post  on  block  with 
post  I  of  coil ;  connect  post 
2  of  coil  with  one  pole  of 
dry  cell ;  and  fasten  an  in- 
sulated wire  to  the  other 
pole.  Now  bend  the  free 
end  of  this  wire  back  on 
itself,  so  that  the  end  shall 
be  smooth  and  rounded.  "See  that  the  wire  is  bright.  If 
this  wire  be  touched  to  any  part  of  the  aluminum  coil  the 
primary  circuit  will  be  made,  and  if  the  wire  is  drawn 
across  the  coils,  a  series  of  making  and  breaking  shocks 
will  be  given. 

a.     Sitmiuatioii  of  Tzuo  Contractions. 

If  two  stimuli  reach  a  muscle  at  a  sufficiently  short  inter- 
val the  second  contraction  process  may  begin  before  the 
first  one  is  completed.  What  will  be  the  result?  In  this, 
as  in  the  preceding  experiments,  each  student  is  to  do  the 
work  independently. 

Experiment. — Blacken    drum    and    arrange    for    quick 

speed ;  make  a  muscle  preparation  and  mount  it  in  moist 

chamber,   as   in   Experiment   3 ;  place   drum   so  that   lever 

will  record  well.     Open  short  circuit  key  ;  with  the  drum 

4 


32  EXPERIMENT  VI. 

still,  excite  the  muscle  by  drawing  free  end  of  wire  con- 
nected with  battery  across  the  last  turn  of  aluminum  wire 
on  block  (Fig.  y,  A)  ;  choose  a  strength  of  induced  current 
which  will  give  a  good  breaking  and  no  making  contraction. 
Let  muscle  rest.  Now  start  drum,  and  draw  wire  across 
windings  a  and  b,  at  such  a  rate  as  to  cause  two  separate 
contractions ;  repeat  several  times,  and  more  quickly  each 
time,  until  the  two  contractions  look  like  one.  Do  not  stop 
the  drum  between  the  tests ;  either  perform  them  in  rapid 
succession,  or  let  the  drum  revolve  several  times,  making 
a  test  with  each  revolution  and  at  such  a  time  that  the 
records  of  the  succeeding  tests  will  follow  each  other.  How 
do  the  records  differ? 

b.  Incomplete  Tetanus  and  Complete  Tetanus. 

Apparatus. — Use  the  same  apparatus  as  in  a,  and  in 
addition  mount  a  time  signal  (chronograph)  so  that  the 
writing  point  will  write  below  and  in  same  vertical  line 
with  the  muscle  lever.  Connect  the  signal  with  the  bind- 
ing posts  on  the  side  of  the  desk.  In  the  time  circuit,  there 
is  a  battery,  and  a  clock  which  interrupts  the  circuit  once 
a  second.  The  signal  should  record  seconds  on  the  drum. 
The  drum  should  run  4  cm.  per  second. 

Experiment. — Make  experiment  as  in  a,  only  this  time 
draw  wire  across  all  the  windings  of  the  aluminum  coil. 
In  doing  this  see  that  the  hand  is  moved  at  an  even  rate 
across  the  coil.  The  experiment  is  a  test  not  only  of  the 
behavior  of  the  frog's  muscle  under  varying  rates  of 
stimuli,  but  your  capacity  to  move  the  hand  constantly  at 
different  speeds,  i.  e.,  muscle  coordination.  State  in  notes 
approximately  the  number  of  excitations  per  second  required 
to  tetanize.  A  complete  tetanus  is  an  apparently  continuous 
contraction  produced  by  a  series  of  excitations.  All  our 
movements  are  tetani. 

c.  Complete  Tetanus  Obtained  ivith  Automatic  Interrupter. 

Apparatus. — The  apparatus  is  the  same  as  in  Experi- 
ment 3,  excepting  that  the  battery  and  key  are  connected 
with  different  posts  of  the  primary  coil. 


GENESIS  OF  TETANUS. 


33 


Electrical  Couiiectiojis  in  Primary  Circuit  of  Induction 
Apparatus. 
Two  kinds  of  coils  are  used  by  the  students.  Model  A 
in  which  the  secondary  coil  slides  on  metal  rods,  and  Model 
B  in  which  the  secondary  coil  slides  on  the  wooden  base. 
The  way  in  which  the  binding  posts  belonging  to  the  pri- 
mary circuit  are  connected  with  the  primary  coil  and  the 
automatic  interrupter  is  different  in  these  two  forms  of 
apparatus. 


..^ 


Fig.  8.  Scheme  of  electrical  connections  of  primary  coil  in  two  forms  of  in- 
duction apparatus.  A,  soft  iron  wires  in  primary  coil;  B,  hammer;  C,  contact 
screw;  I,  2,  3,  binding  posts. 

Model  A — To  obtain  single  making  and  breaking  shocks 
use  posts  I  and  2.     To  obtain  tetanizing  current  use  posts 

1  and  3. 

Model  B — To  obtain  single  making  and  breaking  shocks 
use  posts  I  and  2.     To  obtain  tetanizing  current  use  posts 

2  and  3.  In  each  apparatus  if  single  shocks  are  needed, 
the  battery  and  key  are  connected  with  the  posts  to  which 
the  two  ends  of  the  wire  of  the  primary  coil  are  directlv 
attached.  If  a  long  series  of  rapidly  following  shocks  are 
needed,  as  for  tetanus,  the  battery  and  key  have  to  be  so 
connected  as  to  bring  the  automatic  interrupter  into  the  cir- 
cuit. This  is  done  in  Model  A  by  connecting  the  battery 
with  posts  I  and  3.  The  current  can  then  enter  by  post  3. 
pass  to  the  contact  screw,  down  the  spring,  then  through 
the  wire  of  the  primary  coil,  and  away  by  post  i.  In  Model 
B,  posts  2  and  3  are  used.  The  current  enters  by  post  3. 
passes  to  contact  screw,  down  the  spring,  through  the  coil, 
and  awav  bv  post  2. 


34  EXPERIMENT  VI. 

In  each  case,  as  the  current  flows  through  the  coil  it 
magnetizes  iron  wires  inside  it,  and  the  hammer  is  attracted. 
The  movement  of  the  hammer  breaks  the  contact  between 
the  spring  and  the  contact  screw,  and  the  current  ceases  to 
flow ;  the  soft  iron  wires  lose  their  magnetism,  the  hammer 
is  released,  and  the  spring  again  makes  contact  with  the 
contact-screw.  Thus  the  primary  current  is  being  contin- 
ually made  and  broken,  and  a  series  of  rapidly  following 
induction  shocks  develop  in  the  secondary  coil. 

Notice. — In  order  that  the  automatic  interrupter  may 
work  well,  the  contact-screw  is  screwed  up  until  it  barely 
touches  the  spring  when  at  rest. 

Experiment. — After  the  apparatus  has  been  arranged, 
the  automatic  interrupter  tested,  and  a  fresh  drum  black- 
ened, prepare  a  muscle  and  mount  it  in  the  moist  chamber. 
Now  adjust  lever  to  drum;  see  that  short-circuiting  key 
is  closed ;  close  key  in  primary  circuit ;  start  kymograph 
clockwork  (quick  speed)  ;  open  short  circuit  key  for  a  few 
seconds ;  then  close  short  circuit  key ;  stop  drum  a  few 
seconds  later  and  open  key  in  primary  circuit.  If  the  curve 
does  not  return  to  the  base  line  promptly  when  the  excita- 
tion ceases,  it  is  because  the  after  contraction,  known  as 
"Contracture,"  is  present. 

d.     Fatigue  Caused  by  Tetanus. 

Experiment. — This  experiment  is  to  be  made  in  the 
same  manner  as  c,  excepting  that  the  drum  should  revolve 
slowly  and  the  tetanic  excitation  be  permitted  to  act  on 
the  muscle  until  it  is  completely  fatigued. 


GENESIS  OF  TETANUS.  35 


36 


KXPKRIMF.NT  VI. 


indep]e;ndent  irritability  of  muscle. 


EXPERIMENT  VII. 


Independent  Irritability  of  Muscle. 


Arrange  the  induction  apparatus  for  tetanizing  current, 
and  connect  a  pair  of  copper  electrodes  to  the  secondary 
circuit. 

a.  Experiment. — Kill  a  frog  by  pithing  the  brain, 
(Method  will  be  demonstrated.)  Have  a  pointed  match  at 
hand,  and  as  soon  as  pithing  needle  is  withdrawn  plug  the 
skull  cavity  through  the  foramen  magnum,  to  prevent  loss 

of  blood  and  to  insure  destruc^ 
tion  of  brain.  Slit  the  skin  on 
the  back  of  left  thigh  longitud- 
inally, separate  the  semimem- 
branosus from  the  ileofibularis 
muscle,  and  expose  the  sciatic 
nerve,  (see  Fig.  lo.  Dorsal 
View).  Carefully  separate  a 
portion  of  the  nerve  from  the 
surrounding  tissues  without  in- 
jury to  the  nerve  or  the  blood 
vessels.  Pass  a  ligature  under 
the  nerve,  carrying  the  ends 
around  to  the  front  of  the  thigh,  and  tie  tightly,  thus  in- 
cluding all  the  structures  of  the  limb  except  the  nerve. 
Cover  exposed  nerve  with  filter  paper  moistened  with  salt 
solution. 

Inject  into  the  dorsal  lymph  sac  about  i  cc.  of  a  stock 
solution  of  curara.  Use  for  this  purpose  a  pipette  with 
fine  point  and  rubber  bulb.  To  insert  pipette,  raise  loose 
skin  of  back  over  forward  part  of  dorsal  lymph  sack  with 
forceps,  and  make  small  opening  in  skin  with  scissors.  Lay 
the  frog  on  a  plate  and  cover  it  with  moist  filter  paper.  Ob- 
serve that  pinching  the  toes  of  either  hind  leg  slightly, 
causes  a  contraction  of  the  muscles  of  the  leg  thus  irritated. 
As  the  drug  takes  effect,  the  ability  of  the  right  leg  to  re- 


Fig.  9.  Relation  of  brain  to 
skull  of  frog.  A,  cerebral  hemi- 
spheres; B,  eyes;  C,  thalamen- 
cephalon;  D,  opticlobes;  E,  tym- 
panic membrane;  F,  cerebellum; 
G,  medulla  oblongata;  H,  spinal 
cord. 


38  EXPERT  MEXT    VII. 

spond  to  such  irritation  gradually  becomes  less,  and  after 
20  or  30  minutes  it  ceases  altogether,  although  the  left  leg 
will  respond  as  before. 

When  all  the  body  but  the  left  leg  has  become  com- 
pletely paralyzed,  open  the  abdominal  cavity  and  remove 
the  vicera,  care  being  taken  not  to  injure  the  nerves  behind 
them,  (see  Fig.  10,  \'entral  Mew).  Cut  the  body  in  two, 
leaving  the  last  two  vertebrae  connected  with  the  legs.    Split 

Vkntral  View       Doksal  Vihw 


Fig.  10.  Dissection  ofriglit  leg  of  frog.  A,  sciatic  plexus;  B,  cniralis;  C,  sar- 
torius;  D.  gracilis  magnus;  E,  gastrocnemius;  K.  glutaeus  niagnus;  G,  sciatic 
nerve;  H,  llio-fibularis;    I.  semimembranosus. 


these  vertebrae  lengthwise,  and  holding  the  fragments  with 
forceps,  dissect  out  the  sciatic  plexuses  supplying  the  hind 
legs.  Do  not  take  hold  of  nerves  with  forceps,  and  avoid 
stretching  them.  Fasten  pair  of  electrodes  to  the  posts  of 
secondary  coil.  Stimulate  these  plexuses  in  turn  with  the 
letanizing  current.  What  is  the  result?  Now  apply  the 
stimulus  directly  to  the  muscles  of  the  legs.  What  is  the 
result  ? 


INDEPENDENT   IRRITABILITY   OF    MUSCLE.  39 

Keep  the  preparation,  to  use  in  Experiment  8,  which 
should  immediately  follow  this  one. 

Answer  the  following  questions  in  your  notes,  and  state 
proofs : 

Can  curara  paralyze  before  it  produces  anaesthesia? 

Does  curara  poison  nerve  fibres? 

Does  it  poison  muscles? 

What  does  it  poison? 

How  did  the  drug  reach  the  leg? 

When  an  electric  current  is  sent  through  a  non-cur- 
arized  muscle,  as  in  the  preceding  experiments,  what  two 
kinds  of  stimuli  mav  act  on  the  muscle? 


40  i;xpe;riment  vii. 


INDKPF.NDDNT   IRRITABILITY   OF   MUSCLE-  .41 


EXPERIMENT  VII. 


ISOLATED  CONDUCTION  OF  MUSCLE.  43 

EXPERIMENT  VIII. 

Isolated  Conduction  in  Muscle. 

Although  the  separate  fibers  of  a  striated  muscle  are  in 
close  contact,  they  are  like  the  nerve  fibers  in  a  nerve  trunk, 
independent  mechanisms.  If  a  fiber  is  excited,  the  condition 
of  activity  which  is  aroused  runs  the  length  of  the  fiber 
but  does  not  spread  to  neighboring  fibers.  This  fact  can 
be  demonstrated  most  readily  on  a  curarized  muscle,  and 
by  employing  unipolar  excitations. 

Apparatus  for  Unipolar  Excitation. — Arrange  in- 
duction coil  to  give  tetanic  excitations.  Connect  one 
pole  of  the  secondary  coil  by  an  insulated  wire  with 
the  binding  post  on  the  sheet  of  copper.  The  other  pole 
of  the  secondary  coil  may  be  left  free,  or,  if  a  strong  cur- 
rent is  needed,  be  connected  with  a  gas  pipe  and  so  with 
the  earth. 

Experiment. — Remove  the  sartorius  muscle  (see  Ven- 
tral \'iew.  Fig.  lo),  from  the  curarized  leg  of  the  frog 
used  in  the  Experiment  VII.  Lay  the  muscle  on 
the  copper  plate.  Start  the  automatic  interrupter 
and  touch  one  edge  of  the  muscle  for  a  moment  with 
the  point  of  a  needle  or  other  metallic  instrument  with 
sharp  point.  The  muscle  will  be  seen  to  contract  along  the 
edge  that  is  touched  and  to  curl  towards  that  side.  If  the 
other  edge  be  touched,  the  muscle  will  draw  together  on 
the  other  side.  With  a  reading  glass  one  can  see  that  the 
only  fibers  to  contract  are  those  near  the  point  touched. 
The  current  enters  the  muscle  wherever  it  is  in  contact 
with  the  copper  plate  (the  indififerent  pole),  but  being  diffuse 
fails  to  excite ;  it  leaves  the  muscle,  to  charge  up  the  body 
of  the  experimenter,  at  the  point  that  is  touched  by  the 
needle  (the  active  pole)  and  the  dense  stream  causes  excit- 


44  EXPERIMENT  VI 1 1. 

atioii  at  that  point.  The  strict  Hmitation  of  the  contraction 
process  to  the  fibers  excited,  shows  that  the  excitation  does 
not  spread  from  fiber  to  fiber. 

Why  is   it  necessary   to   supply  a  curarized   muscle   in 
this  experiment? 


ISOLATED  CONDUCTION  OF*  MUSCLE.  45 


46 


i<;xiM',Ki.v;i:N'r  VI II 


CONTRACTIONS  OF   NON-STRIATED   MUSCLES.  47 

EXPERIMENT  IX. 

Contractions  of  Non-Striated  Muscle. 

Apparatus. — Set  up  apparatus  like  that  used  in  b  of 
Experiment  V,  with  the  exception  of  the  foric,  which  is 
replaced  by  a  signal  connected  with  the  clock  circuit,  so  as 
to  give  the  time  in  seconds.  No  weight  should  be  used 
on  the  lever. 

Experiments. — Kill  a  frog,  remove  the  stomach,  cut 
off  from  stomach  a  ring  from  3  to  5  mm.  wide,  and  hang  this 
ring  of  non-striated  muscle  on  a  pin  hook  which  has  been 
fastened  vertically  in  the  clamp  intended  for  femur.  Con- 
nect the  lower  border  of  the  ring  with  the  pin  hook  attached 
to  writing  lever,  and  the  pin  of  pin  electrode.  Keep  moist 
chamber  closed  and  moisten  muscle  frequently,  as  it  is  so 
small  that  it  is  especially  liable  to  be  injured  by  drying. 

a.  Time  Relations  of  Myogram. — Proceed  at  once  to 
determine  the  time  relations  of  non-striated  muscle.  The 
method  given  in  b  of  Experiment  V  is  to  be  used,  with  the 
exception  that  the  drum  is  to  be  revolved  by  the  clockwork, 
and  to  have  a  rate  of  2  mm.  per  second.  See  that  writing 
points  are  in  the  same  vertical  line,  and  put  part  of  curve 
showing  this  in  your  notes.  Find  the  latent  period,  and  the 
time  of  the  rise  of  the  curve. 

b.  Rate  Required  to  Tetanise. — Set  the  drum  turn- 
ing slowly  and  find  by  experiment  slowest  rate  of  stimula- 
tion which  will  tetanize  non-striated  muscle  (see  Experiment 
VI,  b).  In  order  to  tetanize,  a  second  contraction  should 
be  called  out  a  short  time  before  the  preceding  contraction 
has  reached  its  full  height.  If  one  knows  the  latent  period 
and  the  contraction  period,  one  can  make  a  fair  estimate 
of  the  required  rate  of  excitation.  It  may  be  of  advantage 
to  introduce  a  signal  magnet  in  the  primary  circuit  to  mark 
the  time  of  excitation. 

c.  Spontaneous  Contractions. — Set  the  drum  to  run 
at  the  rate  of  i   mm.  per  second  or  slower,  and  record  a 


48  EXPERIMENT  IX. 

series  of  spontaneous  contractions.  L,et  the  time  be  recorded 
in  seconds.  Spontaneous  contractions  may  occur  from  the 
first,  and  interfere  with  the  determination  of  time  relations. 
If  such  is  the  case,  the  only  way  to  secure  the  results  is  to 
give  the  stimuli  at  such  a  time  that  one  can  be  sure  whether 
the  following  contraction  is  a  response  to  the  stimulus  or 
a  spontaneous  contraction. 

How  does  the  latent  period  and  the  contraction  period 
of  this  non-striated  muscle  compare  with  that  of  the  gas- 
trocnemius? What  rates  were  needed  to  tetanize  these 
muscles?  What  was  the  rate  of  the  spontaneous  con- 
tractions ? 


CONTRACTIONS  OP   NON-STRIATED   MUSCLES.  49 


50 


KXPKRIMIvNT  JX. 


WAVE   OF   CONTRACTION    IN    FROGS    HEART.  51 


EXPERIMENT  X. 

Frog's  Heart — Its  Structure,  and  the  Relative  Time  of 
Action  of  the  Different  Parts. 

Apparatus. — Set  up  as  shown  in  Figure  ii.  Clamp 
horizontally  on  short  stand,  the  nickled  rod  with  hole  for 
wire  and  binding  screw  in  end  (A),  letting  the  free  end  of 
the  rod  project  about  7  cm.  beyond  the  stand.  Place  a 
clamp  on  the  end  of  the  rod,  and  fasten  vertically  in  this 
clamp  the  rod  (B)  carrying  the  lighter  muscle  lev- 
er. Thus  arranged  the  lever  can  be  either  raised 
or  lowered,  or  can  be  rotated  so  as  to  bring  the 
point  against  the  drum.  Loosen  the  screw  fastening  the 
yoke  (C)  of  the  lever  to  the  rod,  and  turn  the  yoke  until 
it  supports  the  lever  with  the  tip  2  cm.  below  the  horizontal 
plane  passing  through  its  axis ;  then  turn  the  screw  home. 
Now  bring  the  drum  up  to  the  lever,  and  see  that  when  it 
is  horizontal  it  has  such  a  height  that  it  can  be  made  to 
write  on  any  part  of  the  drum  by  raising  or  lowering  the 
drum.  Clamp  the  frog  board  (G)  to  the  stand  below  the 
lever.  Introduce  into  the  fourth  hole  of  the  lever  the  short 
piece  of  copper  wire  (B)  with  cork  button  at  the  end,  and 
fasten  the  piece  of  flexible  insulated  wire  (F)  to  the  binding- 
post  on  the  frog  board.  Observe  that  the  two  wires  which 
project  through  the  button  may,  when  brought  in  contact 
with  the  heart,  be  used  as  electrodes.  Put  time  signal  on 
long  stand,  at  such  a  height  that  it  will  write  just  below 
the  lever  when  it  is  horizontal.  In  this  experiment  the 
signal  will  be  used  only  to  give  a  base  line.  Blacken  the 
drum. 

Operation. — Choose  an  active  frog ;  pith  brain  as 
described  in  Experiment  YII ;  cut  off  the  projecting  end 
of  match ;  and  put  frog,  back  down,  on  the  plate.  Operate 
at  once,  before  the  effects  of  the  shock  have  passed  off.  Make 
median  skin  incision  from  one  half  centimeter  above  pubis  to 


52 


EXPERIMENT   X. 


one  half  centimeter  below  jaw.  Raise  ensiform  cartilage  with 
forceps,  and  with  sharp  scissors  cut  in  median  line  through 
sternum,  pectoral  girdle,  and  muscles  of  throat,  always 
keeping  point  of  scissors  well  away  from  the  pericardium 
and  aortae.  Prolong  incision  .through  abdominal  wall, 
avoiding  the  large  vein.  Slight  haemorrhage  can  be  checked 
with  dry  absorbent  cotton.  Now  slide  the  heart  lever  up 
out  of  the  way,  and  place  the  frog  on  the  frog  board  so 


Fig.  II.  Apparatus  for  recording  the  beat  of  a  frog's  heart.  A,  horizontal 
roil  carrj'ing  binding  screw  for  wire;  B,  vertical  rod  carrying  lever;  C,  yoke  sup- 
porting axis  of  lever;  D,  time  signal;  ii,  copper  wire,  connecting  lever  with 
cork  button  to  rest  on  the  heart;  K,  piece  of  flexible  insulated  wire,  connecting 
short  piece  of  copper  wire,  passing  through  cork  button  with  binding  post 
on  frog  board;  G,  frog  board. 


that  its  ventricle  lies  directly  beneath  the  cork  button  on 
the  prop  of  the  lever.  With  the  frog  in  this  position,  draw 
the  fore  legs  widely  apart  so  as  to  expose  the  heart  beating 
within  the  pericardium,  and  pin  these  legs  firmly  to  the 
frog  board.  Now  pick  up  the  pericardium  over  the  bulbus 
arteriosus,  and  slit  the  pericardium  throughout  its  length 
with  sharp  pointed  scissors. 


WAVE    OF    CONTRACTION    IN    FROGS    HEART. 


53 


a.     G?-oss  Anatomy  of  the  Heart. 

Moisten  the  heart  from  time  to  time  with  normal  salt 
solution  ;  it  must  not  be  allowed  to  dry.  Observe  the  posi- 
tion of  the  bulbus  arteriosus  (H)  and  the  two  aortic  arches 
(A)  ;  the  relation  of  the  two  auricles  (B,  C)  to  each  other 
and  to  the  ventricle  (£).  (the  line  of  separation  of  the 
auricles  lies  behind  the  bulbus  arteriosus)  ;  and  the  well 
marked  auriculo-ventricular  groove.  Lift  the  ventricle  with 
a  camel's  hair  brush  moistened  with  saline  solution,  and 
notice  the  place  where  the  vena  cava  inferior  opens  into 
the  sinus  venosus  (F)  \  the  white  crescentic  line  where  the 


Dorsal  View 


Ventral  View 


b'ig.  12.  The  gross  anatomy  of  frog'8  heart.  (Ventral  view  after  Cyou,  dorsal 
view  after  Howes.)  A,  aortae;  B,  right  auricle;  C,  left  auricle;  D,  pulmonary  vein 
K,  ventricle;  F,  sinus  venosus;  G,  sinu-auricular  valves;  H,  bulbus  arteriosus. 

sinus  joins  the  auricle  ;  also  the  frenum,  a  slender  ligament 
which  attaches  the  dorsal  wall  of  the  ventricle  to  the  peri- 
cardium. 

b.     Origin  and  Course  of  the  JVavc  of  Contraction. 

I. — Inspection. — Try  to  observe  the  place  where  the 
wave  of  contraction  begins,  and  the  order  in  which  it  spreads 
over  the  different  chambers  of  the  heart.  See  that  when  a 
part  contracts  and  drives  the  blood  out,  it  grows  paler, 
while  the  part  receiving  the  blood  swells  and  flushes.  Ans- 
wer in  your  notes  the  following  questions :  What  is  the 
action  of  the  auricles  during  the  ventricular  diastole,  and 
during  the  ventricular  s)'Stole?  What  changes  are  observed 
in  the  ventricle  during  auricular  diastole,  and  during  auric- 
ular svstole? 


54  EXPERIMENT  X. 

2. — The  Myocardiogram. — Adjust  the  cork  on  the 
prop  of  the  lever,  to  the  ventricle,  with  the  prop  vertical  and 
the  lever  horizontal.  Be  careful  that  both  of  the  wire 
points  on  the  under  surface  of  the  cork  are  in  contact  with 
the  ventricle,  and  that  the  cork  does  not  touch  the  auricle 
so  as  to  be  moved  directly  by  it.  Once  rightly  adjusted, 
it  should  not  be  necessary  to  alter  the  position  of  the  lever 
during  the  afternoon.  The  prop  should  be  connected  with 
the  hole  in  the  lever  which  will  give  a  writing  of  one  and  a 
half  to  two  centimeters  in  height.  Record  the  beats  with 
slow,  medium  and  rapid  speeds  of  the  drum,  studying  the 
heart  itself  while  the  curves  are  being  written.  Mark  on  the 
record  the  part  of  the  cardiac  cycle  which  is  responsible  for 
each  wave  of  the  curve.  How  and  why  does  the  beat  of 
the  auricle  show  in  the  curve?  Which  part  of  the  curve 
was  made  by  the  ventricular  systole?  Does  the  lever  fall 
or  rise  in  the  ventricular  diastole?    Explain. 


WAVE   OF   CONTRACTION    IN    FROGS    HEART.  55 


56  KXPERIMKnT  X. 


REFRACTORY   PERIOD. 


EXPERIMENT  XL 

Refractory  Period  and  Compensatory  Pause. 

Apparatus.— The  same  frog  and  the  same  apparatus 
for  recording  the  contractions  of  the  heart  may  be  used  as 
in  the  preceding  experiment.  In  addition  arrange  an  induc- 
tion coil  to  give  single  shocks,  placing  a  time  signal  in  the 
primary  circuit,  and  arranging  it  to  write  just  below  and 
in  the  same  vertical  line  with  the  heart  lever.  One  cell  in 
the  primary  circuit,  with  the  secondary  coil  pushed  half 
way  up,  usvially  gives  sufficient  strength  of  current.  One 
of  the  wires  from  the  secondary  coil  is  to  be  fastened  to 
the  binding  post  on  the  frog  board,  and  be  brought  in  com- 
munication with  the  ventricle  by  means  of  the  fine  insulated 
wire  passing  to  one  of  the  pins  in  the  piece  of  cork  resting 
on  the  ventricle  (see  Fig.  1 1 )  ;  the  other  wire  is  to  be  fastened 
to  the  horizontal  rod  supporting  the  heart  lever,  through 
which  it  communicates  with  the  heart. 

Experiment. — When  all  is  ready,  mark  the  relative 
position  of  the  writing  points  on  the  drum.  Don't  forget 
that  unless  this  is  done,  and  the  length  of  the  lever  is  given 
in  the  notes,  the  experiment  will  not  be  accepted.  Also, 
either  before  or  after  the  experiment,  place  the  lever  hor- 
izontal, and  let  it  record  a  base  line  to  be  used  in  measuring 
the  curve.  Let  the  drum  run  at  the  rate  of  20  mm.  per  sec- 
ond. While  the  heart  records  its  contractions  , stimulate  the 
ventricle  with  single  breaking  shocks  every  fifth  or  sixth 
beat,  the  makes  being  short  circuited,  to  test  the  effect  of 
exciting  it  at  the  following  times, — during  the  systole  of 
the  ventricle,  and  early  and  late  in  the  diastole  of  the 
ventricle. 

State  in  notes  in  which  case  the  stimulus  produces  no 
effect  (the  "Refractory  period'')  ;  when  it  produces  a  con- 
traction of  increased  height ;  when  an  extra  contraction  of 
less  height  than  usual ;  and  when  one  of  usual  height.  No- 
tice that  an  extra  contraction  is  followed  by  a  pause.     Is 


58  EXPERIMENT  XL 

the  pause  long  enough  to  compensate  for  the  extra  contrac- 
tion, so  that  the  rhythm  of  the  beat  is  not  changed  after- 
ward ?  Such  a  pause  is  called  a  "Compensatory  pause." 
and  is  explained  on  the  theory  that  the  irritability  of  the 
ventricle  is  lessened  by  its  extra  contraction,  so  that  it  can- 
not respond  to  the  stimulus  which  comes  to  it  from  the 
auricle  at  the  usual  time  for  the  next  beat.  Can  you  detect 
a  beat  of  the  auricle  at  the  time  it  usually  comes,  during 
the  compensatory  pause? 

The  curve  of  contraction  is  distorted  by  the  fact  that 
the  lever  records  an  arc.  To  determine  the  part  of  a  con- 
traction at  which  a  stimulus  was  applied,  it  is  necessary  to 
draw  a  vertical  line  through  the  point  of  excitation  as  given 
by  the  time  signal,  to  a  base  line  which  corresponds  to  the 
position  of  the  heart  lever  when  horizontal,  and  then  hav- 
ing allowed  for  the  relative  position  of  the  writing  points, 
to  draw  through  the  heart  curve  an  arc.  the  axis  of  which 
is  on  this  base  line  and  the  radius  of  which  is  equal  to  the 
length  of  the  lever. 


RKFRACTORY  PERIOD.  59 


6o  EXPERIMENT  Xr. 


EXCITATION    OF    THE    RESTING    HEART.  6 1 


EXPERIMENT  XII. 

Response  of  the  Resting  Heart  to  Stimulation  by  Induc- 
tion Shocks. 

Apparatus. — Use  apparatus  the  same  as  in  Experiment 
XI,  and  in  addition,  mount  a  tuning  fork  on  large  stand 
above  the  electric  signal.  Be  sure  that  the  writing  points 
are  in  the  same  vertical  line.  Prepare  a  frog,  and  expose 
heart,  losing  as  little  blood  as  possible. 

Experiment. — Bring  heart  to  rest  by  tying  a  ligature, 
the  first  Stannius  ligature,  about  the  juncture  of  the  sinus 
with  the  auricles.  To  do  this  pass  ligature  under  the  aortic 
arches  close  to  the  auricles,  then  pass  the  ends  around  the 
heart  posteriorly  so  that  the  ligature  lies  at  the  base  of  the 
auricles,  and  tie  a  single  knot  loosely  over  the  crescentic 
line  where  the  sinus  and  the  auricles  join.  Make  sure  that 
the  ligature  is  in  the  proper  place,  then  tighten  and  tie 
securely.  The  heart  should  stop  beating.  If  it  does  not  do 
so  within  a  few  seconds,  tie  a  second  ligature  closer  to  the 
auricles. 

a.     Myogram  of  Heart  Muscle. 

As  soon  as  the  beat  stops,  place  frog  on  board  and  con- 
nect heart  with  lever.  Move  coil  far  away,  and  find  small- 
est stimulus  that  will  cause  a  contraction ;  then  mark  on 
drum  relative  position  of  writing  points  ;  finally  record  the 
curve  of  contraction  and  beneath  it  the  tuning  fork  curve, 
and  the  moment  of  make  and  break  of  the  primary  circuit, 
as  shown  by  the  signal.  Turn  the  drum  by  hand  at  rate  of 
about  lo  cms.  per  second.  Assume  that  the  signal  records 
the  exact  moment  of  excitation,  and  calculate  from  the  rec- 
ord the  time  relations  of  the  myogram,  as  in  Experiment  V. 
Save  a  part  of  the  record  which  shozvs  that  the  zvriting 
points  are  in  the  same  vertical  line,  and  state  in  notes  length 
of  lever  in  millimeters.  In  what  respect  does  the  myogram 
obtained  from  the  heart  diflfer  from  that  of  striated  muscle? 


62  EXPERIMENT   XII. 

b.  Bozi'ditch's  Staircase. 

As  soon  as  a  sufficient  number  of  myograms  have  been 
recorded,  remove  the  fork,  and  stimulate  about  15  times 
with  same  strength  of  current  at  intervals  of  5  seconds, 
recording  on  drum  moving  2  mm.  per  second.  A  gradually 
increasing  height  of  contraction  is  usually  given,  which  is 
called  a  staircase,  and  explained  as  a  result  of  increased 
irritatibility  due  to  frequent  repetition  of  the  stimulus. 

c.  All  Contractions  Maximal. 

Now  stimulate  about  ten  times  with  gradually  increas- 
ing current  at  intervals  of  30  seconds,  recording  contractions 
on  drum  about  i  cm.  apart.  There  is  no  increase  in  height 
of  contraction  due  to  increased  stimulus.  Any  stimulus 
sufficient  to  cause  heart  muscle  to  contract  causes  a  maximal 
contraction.  This  is  often  spoken  of  as  the  law  of  "All 
or  none." 

d.  Bifcct  of  Frequent  Stimuli. 

Connect  wires  of  primary  circuit  with  automatic  inter- 
rupter and  record  the  response  of  the  heart  to  frequent 
stimuli,  using  first  a  weak  and  then  a  medium  current.  Drum 
should  turn  5  mm.  per  second.  Weak  stimuli  should  cause 
separate  beats  and  stronger  stimuli,  increase  of  tonus,  indi- 
cated by  a  higher  base  line. 


EXCITATION    OF    THE   RESTING    HEART.  63 


54  EXPERIMENT   XII. 


MOTOR   POINTS  ON   THE   ARM.  65 

EXPERIMENT  XIII. 

Location  of  a  Few  Motor  Points  on  the  Human  Arm. 

The  few  motor  points  surrounded  by  a  circle  in  the  dia- 
gram (Fig.  15),  are  to  be  located  on  each  arm.  In  doing 
this,  the  unipolar  method  of  excitation  is  to  be  employed. 
To  use  this  effectively,  the  more  efficient  pole  of  the  induc- 
tion coil  will  have  to  be  used. 

The  more  Efficient  Pole  of  an  Induction  Coil. — 
When  the  manner  of  winding  and  connecting  wires  with 
posts  can  be  plainly  seen,  the  direction  of  induced  currents 
can  be  found  easily,  for  the  direction  of  the  primary  cur- 
rents can  be  observed  by  inspection  of  the  battery  and  its 
connections,  and  the  induced  current  flows  in  the  opposite 
direction  to  the  battery  current  at  the  time  of  the  make,  and 
in  the  same  direction  at  the  time  of  the  break.  But  in  most 
coils  the  windings  and  connections  are  hidden,  making  it 
necessary  to  determine  the  point  in  question  in  some  other 
way. 

Connect  a  dry  cell  with  a  key  and  a  pair  of  platinum 
electrodes  as  shown   in   Figure   13.     Lay  a  small  piece  of 

filter  paper  on  a  clean  plate, 

^  (f?^""""' '"■^--M ^^^^     slightly     moisten     it 

'C~~-~-'^^*~~- --'-''^"^    c  with  only   a   few  drop*^  of 

,         ,  a  solution  of  starch  and  po- 

Fig.  13.     Apparatus  to  detect  direction  .  .      ,.  ,  -^ 

of  flow  of  current   in   a  simple  circuit.         taSSUUll    lodldc.       Draw    the 
A,  dry  cell;  B,  mercury  key;  C,  electrode.  1  r      1         1 

ends  of  the  electrodes  slow- 
ly and  lightly  across  the  moistened  paper,  first  with  the 
circuit  open  and  then  with  it  closed.  Observe  the  dark  line 
given  at  the  anode  while  the  current  is  passing,  and  the  ab- 
sence of  color  at  the  kathode.  The  current  decomposes  the 
potassium  iodide,  and  the  iodine,  being  the  acid  ion.  goes 
to  the  anode  and  there  gives  the  color  reaction  with  the 
starch. 

Now  connect  the  cell  to  the  primary  coil  of  induction 
apparatus,  the  anode  v^^ith  post  i  and  kathode  with  post  2. 


66 


EXPERniENT  XIII. 


Connect  the  platinum  electrodes  to  the  posts  of  the  second- 
arv  coil.  Place  the  ends  of  the  electrodes  on  the  moistened 
paper  and  make  the  primary  circuit,  then  slide  the  electrodes 


Kig.  14.  Apparatus  to  detect  direction  of  flow  of  current  in  secondary  coil 
of  an  induction  apparatus.  A,  dry  cell;  B,  mercury  key;  C,  primary  coil; 
U,  secondary  coil;  E,  electrode. 

lo  a  fresh  place  and  break.  A  dark  dot  will  be  given  at  one 
pole  on  making  and  at  the  other  on  br.eaking,  but  no  effect 
will  be  seen  during  the  time  the  primary  current  is  flowing. 
Remembering  that  the  color  reaction  indicates  the  anode, 
we  can  determine  the  direction  of  the  current  in  the  second- 
ary circuit  when  the  primary  is  made  and  when  it  is  broken. 
Since  the  excitation  developed  at  the  kathode  where  the 
current  leaves  the  tissue,  is  stronger  than  that  developed  at 
the  anode  where  the  current  enters  it,  and  since  the  break 
induction  shock  is  stronger  than  the  make,  it  follows  that  the 


Fig.  15.  Diagram  of  location  of  motor  points  on  flexor  side  of  arm.  (After 
Erb.)  A,  median  nerve  in  upper  arm;  B,  flexor  longus  policis;  C,  median  nerve 
at  wrist;  D,  ulnar  nerve  in  upper  arm;  E,  ulnar  nerve  in  groove  between  the 
internal  condyle  of  the  humerus  and  the  olecranon  process;  F,  flexor  profundus 
digitorum;  G,  flexor  sublimis  digitorum;  H,  ulnar  nerve  at  wrist;  I,  abductor 
minimi  digiti. 

more  efficient  pole  of  the  secondary  circuit  is  the  one  that 
is  the  kathode  when  the  primary  circuit  is  broken.  Make 
a  note  of  this  point,  stating  whether  the  more  efficient  pole 
is  the  one  to  which  the  short  circuit  kev  is  attached  or  the 


MOTOR   POINTS  ON   THE  x\RM. 


67 


opposite  one.  Of  course  it  must  be  remembered  that  these 
are  correct  only  when  the  primary  circuit  is  connected  as 
directed  here. 

Pre;paration  op  Skin. — Since  the  epidermis  when  dry 
offers  great  resistance  to  the  current,  it  is  necessary  to 
moisten  it  thoroughly.  For  this  purpose  use  a  warm  sok:- 
tion  of  com^mon  salt  and  borax.  The  solution  can  be 
warmed  in  a  granite  dish,  standing  on  a  tripod  over 
a  gas  flame.  Apply  the  solution  with  a  sponge  or  cloth 
to  the  parts  to  be  stimulated  at  intervals  of  a  few  min- 
utes ;  or  a  pad  soaked  in  the  solution  may  be  bound 
on  and  left  10  or  15  minutes.  Unless  the  skin  is  thoroughly 
moistened,  the  stimuli  are  apt  to  be  painful  and  inefficient. 
Do  not  spill  the  solution  on  tables  or  apparatus. 

Apparatus. — Connect  two  dry  cells  and  a  key  to  the 
primary  coil  of  an  induction  apparatus,  and  connect  a  large 
copper  plate  (the  indifferent  electrode),  to  the  least  efh- 
cient  pole  of  the  secondary  coil,  and  a  small  electrode  (the 
active  electrode),  to  the  more  efficient  pole. 


►^ 

-|              n 

^ -J 

J        D       U 

d 

-1/ — — — Q^~Q)' 


Fig.  16.  Apparatus  for  unipolar  excitation  of  human  nerves.  A,  battery;  B, 
mercury  key;  C,  primary  coil;  D,  secondary  coil;  E,  copper  plate  used  as  indif- 
ferent electrode;  F,  exciting  electrode. 

Experiment. — Locate  the  motor  points  on  the  left  arm 
first.  Fasten  with  elastic  band  the  copper  plate  on  the  back 
of  the  left  hand,  putting  a  wet  gauze  pad  between  to  pre- 
vent the  metal  from  touching  the  skin.  Hold  the  stimulat- 
ing electrode  in  the  right  hand  and  press  it  firmly  upon  the 
skin  at  the  point  to  be  stimulated.  Let  your  companion 
make  and  break  the  circuit,  first  with  the  secondary  coil 
moved  far  away  and  then  with  it  closer  to  the  primary, 
until  a  position  of  the  coil  is  found  that  gives  a  moderate 
stimulus.  As  soon  as  a  suitable  stimulus  is  found,  try  to 
establish  on  your  own  arm  the  motor  points  corresponding 
to  those  marked  with  a  circle  in  the  diagram.     Find   for 


(8  EXPERIMENT  XIII. 

each  point  the  position  of  the  electrode  at  which  the  best 
motor  response  is  given.  The  stimulating  electrode  must 
be  kept  well  moistened.  If  a  good  contraction  cannot 
be  obtained  without  the  sensation  being  painful,  it  indi- 
cates either  that  the  epidermis  is  not  sufficiently  moistened 
or  that  the  right  position  for  stimulation  has  not  been  found. 
Locate  carefully  the  motor  points  on  both  arms  of  each 
student.  Mark  the  points  on  the  skin.  Demonstrate  to 
instructor.     No  notes  are  required. 


MOTOR   POINTS  ON   THR  ARM.  69 


yo  EXPERIMENT  XIII. 


ELECTRICAL  EXCITATION   OF  HUMAN   MUSCLE. 


71 


EXPERIMENT  XIV. 

Response    of    Human     Muscle     to     Separate     Induction 
Shocks  and  to  a  Tetanizing  Current. 

Wet  the  left  arm  over  the  motor  point  for  the  flexor 
longus  pollicis,  bind  on  a  wet  pad,  and  then  arrange  the  ap- 
paratus. See  that  the  hands  are  dry  in  handling  the  appar- 
atus. 

Apparatus. — This  consists  of  an  arm  rest,  recording 
instruments,  and  the  stimulating  outfit  used  in  Experiment 
XIII.  The  arm  rest  is  to  be  placed  on  the  table  before 
which  the  subject  is  to  stand,  with  the  recording  apparatus 
to  the  left,  and  the  stimulating  outfit  to  the  right,  with  key 
and   coil   within   easv   reach  of  his   hand.     The   arm   is   to 


Fig.  17.  Arm  rest  for  support  of  hand  and  electrodes.  A,  arm  rest;  B,  hori- 
zontal rod  fixing  hand;  C,  vertical  rod  on  arm  rest;  D,  copper  plate,  the  indif- 
ferent pole,  on  which  is  the  gauze  pad;  E,  exciting  electrode;  F,  vertical  rod, 
clamped  to  horizontal  rod  on  the  arm  rest. 

lie  in  supination  on  the  arm  rest,  and  the  hand  is  to  be  fixed 
by  a  horizontal  rod  (B)  which  presses  lightly  on  the  palm, 
and  is  clamped  to  the  vertical  rod  on  the  arm  rest. 

The  movement  of  the  thumb  is  to  be  transmitted  by  a 
thread,  which  is  fastened  by  a  loop  to  the  thumb  and  passes 
round  a  pulley  to  a  lever,  which  is  connected  by  another 
thread  to  a  rubber  band  supported  on  an  L  rod,  clamped 
to  the  same  stand  as  the  lever  and  above  it.  The  thread 
from  the  thrmib  is  fastened  to  the  second,  and  that  from  the 


72 


EXPERIMENT   XIV. 


finger  to  the  third  hole  in  the  lever.  When  the  flexor  longus 
pollicis  contracts,  the  lever  will  be  drawn  down,  and  when 
it  relaxes  the  rubber  band  will  pull  the  lever  upwards  .  A 
time  signal  is  to  be  placed  in  the  primary  circuit  of  the 
induction  apparatus,  and  an  indifferent  and  a  stimulating 
electrode  connected  with  the  posts  of  the  secondary  coil. 
The  copper  plate  (Fig.  17,  D), 
which  is  to  act  as  the  indifferent 
pole,  is  to  lie  on  the  arm  rest  in 
such  a  position  that  the  back  of  the 
hand  will  press  on  a  wet  pad  placed 
over  the  plate.  Care  must  be  taken 
that  the  pad  does  not  come  in  con- 
tact with  the  vertical  rod  on  the 
arm  rest.  The  active  pole  (E)  in- 
stead of  being  held  in  the  hand,  is 
to  be  fastened  above  the  arm  in  a 
clamp  on  a  horizontal  rod,  which 
in  turn  is  clamped  to  a  vertical  rod 
(F),  which  is  supported  by  a  clamp 
fastened  to  the  horizontal  rod  at 
the  side  of  the  arm  rest.  This  ar- 
rangement permits  the  exciting 
electrode  to  be  fastened  at  any  de- 
sired point  on  the  arm. 


Lnj> 


Kig.  18.  Apparatus  for  re- 
cording movement  of  thumb. 
G,  rubber  band  supported  by 
Iv  rod;  H,  recording  lever;  I, 
time  signal;  J,  pully;  K, 
thread  to  thumb. 


a.     Making   and   Breaking   Induction   Shocks   of    Various 
Strengths. 

Experiment. — Put  the  wet  pad  on  the  indifferent  elec- 
trode ;  then  place  the  arm  on  the  arm  rest,  so  that  the  back 
of  the  hand  rests  on  the  pad ;  and  fix  the  hand  by  fastening 
the  horizontal  rod  across  the  palm.  Adjust  the  active  elec- 
trode over  the  motor  point  of  the  flexor  longus  pollicis  mus- 
cle. Connect  the  thread  to  the  thumb,  and  move  the  arm 
rest  so  that  the  thread  shall  have  the  proper  position  with 
respect  to  the  pulley,  and  the  elastic  band  be  slightly 
stretched.  Place  drum  in  position.  The  lever  should  now 
be  about  horizontal,  and  flexion  of  the  finger  cause  it  to 
write  well  on  the  drum.     The  subject  handles  the  key  and 


ELECTRICAL  EXCITATION   OF  HUMAN   MUSCLE-  73 

coil  while  his  associate  has  charge  of  the  kymograph,  and 
turns  the  drum  by  hand.  To  stimulate,  close  the  key, 
wait  2  or  3  seconds,  then  open,  and  wait  lo  seconds.  The 
student  attending  to  the  kymograph  should  keep  the  time 
with  his  watch  and  tell  the  subject  when  to  stimulate.  Be- 
gin with  the  coil  placed  so  as  to  give  no  effect,  and  move 
it  up  a  short  distance  after  each  time  the  circuit  is  broken. 
The  signal  marks  the  time  of  slimulation,  and  thus  shows 
what  stimuli  fail  to  give  contractions.  In  case  insufficient 
current  is  obtained,  cut  out  the  time  signal.  Unless  the 
current  causes  too  much  discomfort,  continue  until  both 
making  and  breaking  contractions  of  fair  size  are  recorded. 
During  the  experiment  the  arm  should  be  completely  re- 
laxed. Vohmtary  movemicnts  should  be  avoided  as  far  as 
possible,  and  should  be  noted  when  they  occur. 
b.     Tetaiiizing  Current. 

Apparatus. — Connect  battery,  key,  and  signal  with  the 
automatic  interrupter  of  the  induction  coil. 

Experiment. — Moisten  electrodes.  Choose  strength  of 
current  sufficient  to  cause  a  tetanic  contraction.  Start  drum 
at  fast  speed  and  obtain  a  record. 


74  EXPERIMENT   XIV. 


KLKCTRICAL  I;XCITATI0N   OF  HUMAN   MUSCI,E.  75 


76  EXPERIMENT   XIV. 


GALVANl's   EXPERIMENT.  77 

EXPERIMENT  XV. 
Galvani's  Experiment. 

Arrange   apparatus   as   shown   in  the   diagram,   making 

sure  that  the  zinc  rod  and  brass  hook  are  bright  and  clean. 

Kill  a  frog,  open  the  abdomen,  and 

remove  the  viscera  from  the  posterior 

part,    taking    care    not    to    injure    the 

^   ^  nerves.      Cut   the   body   in   two   trans- 

y        versely  ^  cm.  above  the  point  of  exit 

of  the  nerves  from  the  spinal  column. 

Remove  the  skin  from  the  lower  part 

of  the  body,  cut  a   small   slit  through 

B  the  back   between   the  nerves   and   the 

spine,  and  hang  the  preparation  by  this 

slit  upon  the  brass  hook.     Adjust  the 

zinc  rod  so  that  upon  giving  the  prep- 

„.          ,  aration   a  slight  swing  the  outside   of 

Fig.ig.    Apparatus  ^  ^  .,,.,. 

for  Galvani's    experi-      tlic  thigh  near  the  kucc  Will  stnkc  it. 

ment.    A,    brass    hook,         r,  ,  •  •        •  tt 

supported  on  L  rod;  B,      Set   the   preparation   swinging.      Upon 

zinc  rod.  ,  i  r      i         i  •       j     ,i 

each  touch  of  the  leg  against  the  zinc 
rod  a  contraction  should  occur,  throwing  the  preparation 
away,  and  this  should  be  repeated  every  time  the  swing 
brings  the  leg  against  the  zinc. 

We  have  here  two  unlike  metals  moistened  by  a  liquid 
which  is  practically  continuous  through  the  tissues  of  the 
preparation ;  in  other  words,  we  have  the  essentials  of  what 
is  called  a  Galvanic  battery.  This  experiment  is  of  consid- 
erable historical  interest,  for  it  was  the  observation  of  the 
contraction  of  frogs'  muscles  in  a  similar  case  that  led 
Galvani  to  make  his  famous  studies  of  what  he  supposed 
to  be  animal  electricity,  and  which  was  followed  later  by 
the  invention  of  the  first  battery  by  Volta. 

We  see  here  that  a  battery  current,  like  an  induced  cur- 
rent, is  able  to  excite  muscle.     In  the  next  few  experiments 


cO 


jS  EXPERIMENT  XV. 

the  effects  of  the  direct  battery   current   upon  nerve   and 
muscle  will  be  observed.     Save  the  preparation  for  the  next 
experiment,  if  made  the  same  day. 
No  notes  required. 


c,A],vANrs  i;xperim]<;nt.  79 


8o  EXPERIMENT  XV. 


POLARIZATION   OF  ELECTRODES. 


EXPERIMENT  XVI. 


Polarization  of  Electrodes. 


a.     Polarizable  Electrodes. 

Apparatus. — Arrange  apparatus  as  shown  in  Fig.  20. 
Use  an  electric  light  switch  as  a  short-circuiting  key,  fasten- 
ing two  wires  to  each 
binding  post.  One  wire 
from  each  post  of  the  key 
is  to  be  connected  with  a 
post  on  the  outside  of  the 
moist  chamber,  and  one 
wire  from  each  post  of  the 
key  is  to  be  connected  with 
the  battery.  Until  every- 
thing is  ready,  however, 
leave  one  end  of  one  of  the 
battery  wires  disconnected. 
Fasten  two  short  wires  to 
the  posts  inside  the  moist 
chamber  and  place  the 
free,  bare  ends  so  that  a 
nerve  can  be  laid  across 
them,  i.  e.,  arrange  these 
wires  to  be  used  as  polar- 
izable electrodes.  It  is 
best  to  have  the  connections  with  the  battery  so  that,  when 
the  short-circuiting  key  is  open  and  the  battery  circuit  is 
closed,  the  anode  will  be  nearest  the  muscle,  and  an  ascend- 
ing current,  i.  e.,  away  from  the  muscle,  will  flow  through 
the  nerve. 

Experiment. — Make  a  nerve-muscle  preparation  from 
the  frog  used  in  the  preceding  experiment,  (method  of  mak- 
ing preparation  will  be  demonstrated)  ;  place  the  prepara- 
tion in  the  moist  chamber,  and  let  the  nerve  rest  across  the 


Fig.  20.  Apparatus  tor  observing  polar- 
ization of  electrodes.  A,  nerve;  B,  bare 
copper  vsrires;  C,  electric  light  switch 
used  as  short  circuiting  key;  D,  battery. 


82  EXPERIMENT  XVI. 

two  copper  wires.  Bring  the  writing  point  of  the  lever 
against  a  drum,  and  arrange  the  kymograph  to  turn  the 
drum  2  mm.  per  second.  Start  the  kymograph,  and  let  it 
run  continuously  until  the  end  of  the  experiment.  With 
key  closed,  connect  wire  with  battery,  and  then  open  the 
key  and  let  the  current  flow  through  the  nerve  for  thirty 
seconds  ;  ( uiark  the  contraction  ivhich  should  occur  zvhcn 
the  key  is  opened,  c,  because  the  current  has  been  closed 
through  the  nerve)  ;  now  disconnect  the  wire  from  the  bat- 
tery ;  (mark  the  contraction,  if  any  occurs,  o)  ;  then  begin 
closing  and  opening  the  key  regularly,  once  a  second.  If 
contractions  result,  continue  until  they  cease.  Notice  wheth- 
er the  contractions  are  given  on  closing  or  on  opening  the 
key.  or  both,  and  mark  them  accordingly,  C  and  0,  since 
it  is  now  the  polarization  current  which  is  closed  and  opened. 
Notice  carefully,  throughout  the  experiment  any  change 
in  the  contraction  following  closing  and  opening  the  cir- 
cuit. The  contractions  observed  after  the  battery  has  been 
disconnected  are  caused  by  a  current  going  in  the  opposite 
direction  from  the  battery  current,  i.  e.,  a  descending  cur- 
rent. This  current  results  from  electrolysis  which  has  taken 
place  at  the  points  of  contact  of  the  nerve  with  the  wires. 
The  condiiion  set  up  at  these  points  by  the  passage  of  the 
battery  current  is  the  same  as  that  seen  in  a  storage  battery, 
and  the  wires  are  said  to  be  polarized.  In  order  to  avoid 
such  disturbing  currents  it  is  necessary,  whenever  the  direct 
current  is  used  as  a  stimulus,  to  employ  non-polarizable 
electrodes  . 

b.     Non-Polaricable  Electrodes. 

Ai'PARATus. — The  non-polarizable  electrodes  used  in 
this  course,  consist  of  two  boot-like  pieces  of  porous  baked 
claw  hollowed  at  the  top  to  hold  a  solution  of  zinc  sulphate, 
in  which  two  small  pieces  of  zinc  are  immersed.  The  boots 
of  the  non-polarizable  electrodes  should  have  stood  for  some 
lime  in  physiological  salt  solution,  so  that  they  are  thorough- 
ly saturated  with  it  at  the  time  they  are  employed.  When 
they  are  to  be  used,  dry  the  glazed  tops  thoroughly  ;  put  the 
metal  clips  on  the  tops  of  the  boots ;  fasten  the  clips  on  a 


POLARIZATION   OF   ELECTRODES. 


83 


glass  rod  ;  and  fix  the  rod  in  a  clamp  on  the  support  which 
holds  the  muscle  clamp,  in  the  moist  chamber.  Dry  the 
wires  just  used  as  electrodes,  and  connect  them  to  the 
zincs ;  with  a  dropper  put  about 
half  a  cubic  centimeter  of  zinc  sul- 
phate into  the  boots,  being  careful 
not  to  spill  any  of  it  on  the  outside 
of  the  electrodes.  Then  insert  the 
zincs  into  the  tops  of  the  boots. 

Experiment. — Lay  the  nerve 
across  the  tips  of  the  boots  and  re- 
peat the  experiment  made  before. 
If  the  electrodes  are  not  polariza- 
ble,  closing  and  opening  the  bat- 
tery circuit  should  give  the  same 
effect  as  before,  but  there  should 
be  no  response  to  the  movements 
of  the  key  which  follows. 

On  completing  the  day's  work, 
the  non-polarizable  electrodes  must 
be  thoroughlv   washed  and  soaked 


Eig.  21.  Method  of  arrang- 
ing non-polarizable  boot  elec- 
trodes in  moist  chamber.  A, 
zinc;  B,  porcelain  boot;  C, 
nerve;  D,  wires  to  short- 
circuiting  key. 


over  night  in  normal  salt  solution. 


Pfliiger's  Law. 

The  polarization  current  which  is  set  up,  is  strongest  at 
first  and  gradually  fades  away ;  consequently  in  the  course 
of  an  experiment,  the  student  often  sees  the  effects  of  the 
opening  and  closing  of  strong,  medium,  and  weak  currents. 
These  effects,  which  differ  with  the  direction  in  which  the 
current  flows  through  the  nerve,  have  been  classed  under 
what  is  known  as  Pfliiger's  law.  To  recall  this  law  one 
has  only  to  remember  the  following  facts,  viz.:  i,  that  the 
closing  excitation  develops  in  the  region  of  the  kathode,  and 
the  opening  excitation  near  the  anode ;  2,  that  the  closing 
excitation  is  the  stronger;  3,  that  by  strong  currents  the 
conductivity  of  the  nerve  is  lessened  at  the  anode  during 
the  flow  of  the  current,  and  at  the  kathode  at  the  instant 
that  the  current  ceases ;  4,  with  an  ascending  current  the 


84 


EXPERIMENT  XVI. 


anode  is  nearer  the  muscle,  and  with  a  descending  current 
the  kathode  is  nearer  the  muscle.  The  law  was  tabulated 
as  follows : 


Ascending 

Descending 

Close      Open 

Close       Open 

Weak....... 

Medium.  . . . 

Strong 

+          - 

-\-          — 
+           + 
+           - 

i>OT<ARrzA'riON  OF  electrode;s.  85 


EXPERIMENT  XVI. 


KI'SPONSE  OF  NERVE  TO  DIRECT  CURRENT. 


EXPERIMENT  XVII. 


Response    of    Nerve    upon    Closing    and    Opening    the 

Direct  Battery  Circuit  with   Currents  of 

Various  Strengths. 

Apparatus. — Use  the  ordinary  apparatus  for  recording 
muscle  contractions.     Introduce  a  rheocord  into  the  circuit 

used  in  the  last  ex- 
periment, making 
connections  as  in- 
dicated in  Fig.  22. 
Mount  a  pair  of 
n  o  n  -  p  o  larizable 
electrodes,  in  the 
moist  chamber, 
connecting  the 
wires  so  that  the 
current  will  ascend 
the  nerve.  Observe 
that  the  current 
passes  down  the 
fine  German  silver 
wire  of  the  rheo- 
cord to  the  slider 
and  there  divides, 
part  going  to  the 
nerve  and  part  go- 
ing through  the 
lower  part  of  wire. 
At  the  double  post 
at  bottom  of  wire 
the  two  streams  of  the  current  imite  again  and  pass  togeth- 
er to  the  battery.  Observe  that  the  current  traversing  the 
nerve  must  increase  as  the  slider  is  moved  upward,  because 
the  resistance  in  the  wire  beyond  the  point  where  the  circuit 
divides  is  increased. 


Fig.  22.  Method  of  using  rheocord.  A,  german 
silver  wire;  B,  slider;  C,  double  binding  post  at 
lower  end  of  german  silver  wire;  D,  battery;  E, 
key;  E,  nerve  bridging  the  boot  electrodes,  the 
current  being  ascending. 


88  EXPERIMENT  XVII. 

Experiment. — Since  the  direct  current  rapidly  changes 
the  irritabiHty  of  a  nerve,  the  following  Cautions  must  be 
observed : 

I. — Do  not  apply  the  current  at  all  except  when  you 
wish  a  record. 

2. — Do  not  let  the  current  flow  longer  than  is  absolutely 
necessary. 

3. — Obtain  the  record  by  comparatively  few  stimulations. 

4. — Do  not  excite  oftener  than  once  in  15  seconds. 

Move  the  slider  to  the  bottom,  then  close  and  open  the 
key.  There  should  be  no  response.  Move  slider  up  2  or 
3  cm.  and  repeat.  Continue  in  this  manner,  and  mark  on 
the  curve  the  positions  of  the  slider  at  which  minimal  and 
maximal,  closing  and  opening  contractions  were  obtained. 
Record  as  in  Experiment  III.  Did  the  closing  or  opening 
contraction  appear  first?  Did  Wundt's  closing  or  Ritter's 
opening  tetanus  show?  If  your  preparation  reacts  well, 
and  if  you  like,  you  may  observe  the  facts  tabulated  as 
Pfliiger's  law  (see  Exper.  XVI)  ;  this  is  not  required, 
however. 


RKSPONSlv  or'  NERVK  TO  DIRECT  CURRENT. 


go  EXPERIMENT  xvrr. 


ricsponse;  of  human  nerves  to  direct  current.       91 


EXPERIMENT  XYlll. 

Stimulation  of  Human  Nerves  by  Direct  Current. 

Apparatus. — The  electric  current  of  the  University  is 
used.  (Study  diagram).  It  flows  through  4  lamps,  (which 
let  1.2  amps,  pass)  and  then  is  shunted  round  4  more 
lamps,  and  has  at  the  terminals  A  and  F,  a  voltage  of  220/2 
^iio  volts.  It  then  passes  through  2  lamps  A  and  B, 
(which  let  0.35  amps,  pass)  and  is  shunted  round  3  lamps, 
C,  D,  and  £,  and  has  a  voltage  at  the  terminals  N  and  P, 
of  3  X  1 10/5  =  66  volts. 


Fig.  23.  Apparatus  for  stimulation  of  human  nerves  by  a  direct  current.  A, 
B,  C,  D,  E,  F,  binding  posts  in  second  bank  of  electric  lamps  used  to  cut  down 
the  voltage;  G,  key;  P,  post  where  current  enters,  and  N,  where  it  leaves  rheo- 
stadt;  PP,  post  connected  with  slider,  from  which  current  goes  to  milamme- 
ter;  H,  slider;  I,  milammeter;  J,  commutator  for  reversing  current;  K,  elec- 
trodes; NN,  pole  on  rheostadt  connected  with  N  ind  receiving  current 
returning  from  commutator. 

In  the  rheostadt  it  is  again  shunted,  the  current  passing 
through  the  resistance  from  P  to  A^  and  a  portion  of  it 
heing  led  off  through  the  metal  slider  (H)  to  the  arm  cir- 
cuit. The  resistance  is  equivalent  to  the  German  silver  wire 
of  the  rheocord  used  in  Experiment  XVII.  The  slider  is  con- 
nected with  the  post  PP.  which  gives  the  branch  of  current 
to  the  arm  circuit,  and  the  current  returns  from  this  circuit 


92  EXPERIMENT  XVIII. 

to  post  A'A',  which  is  connected  with  post  A'.  The  amount 
which  goes  to  the  electrodes  varies  with  the  position  of  the 
metal  slider.  Note  that  as  the  slider  is  moved  clockunse  the 
resistance  betzveen  the  slider  and  post  N  increases  and  hence 
more  current  zvill  go  to  the  arm.  A  key  (G)  controls  the  flow 
of  the  current  to  the  rheostadt.  From  terminal  PP  of  the 
rheostadt  the  current  flows  through  a  milammeter  (/),  com- 
mutator (/)  with  cross  wires,  vvhich  permits  the  current  to 
be  reversed,  to  the  positive  electrode,  the  Anode ;  it  then 
flows  through  the  arm  to  the  negative  electrode,  the 
Kathode,  and  back  by  way  of  commutator  to  the  pole  A' A'' 
of  the  rheostadt,  and  thence  to  pole  A'  and  away. 

Experiment. — When  ready  for  this  experiment  report 
to  instructor.  Two  stimulating  electrodes  are  used  in  this 
experiment,  one  being  applied  to  each  arm.  Either  the 
median  or  the  ulnar  nerve  may  be  stimulated,  and  either 
the  motor  point  near  the  elbow  or  the  one  near  the  wrist 
be  used.  Choosing  the  one  which  in  the  preceding  ex- 
periments gave  best  results,  wet  the  places  on  the  two  arms 
thoroughly,  bind  a  wet  pad  on  each,  and  while  the  skin 
is  becoming  saturated,  study  the  apparatus  on  the  main 
table.  See  that  hands  are  dry  zvhen  apparatus  is  handled. 
Using  your  own  induction  coil,  ascertain  again  the  exact 
points  giving  the  best  motor  response.  Mark  these,  and 
then  proceed  to  table  where  experiment  is  to  be  made. 
Bring  slider  against  -flat  side  of  checking-post,  and  see  that 
key  is  open.  Then  place  the  arms  in  the  arm  supports  (see 
Fig.  ly)  and  pressing  the  electrodes  firmly  over  the  motor 
points,  make  the  electrodes  fast. 

In  making  the  experiment  the  subject  sits  quietly, 
watches  for  first  appearance  of  sensation  or  contraction  re- 
sulting from  the  stimuli,  and  reports  at  which  pole  it  occurs. 
The  other  student,  who  is  the  experimenter,  handles  the  key 
and  rheostadt,  reads  the  milammeter.  and  records  the  re- 
sults in  a  table  of  the  following  form,  stating  the  number 
of  milliamperes  required  to  produce  the  eff^ect  sought. 


RESPONSE  OF  HUMAN  NERVES  TO  DIRECT  CURRENT.         93 

TADLE  OF  STRENGTHS  OF  CURRENT  REQUIRED  TO  PRODUCE 
EFFECT. 

Kathode  on hand. 

SENSATION.  CONTRACTION. 

Kathode   closing'    , 

Anode  closing  

Anode  opening  ,  , 

Kathode  opening 


When  all  is  ready  the  experimenter  closes  and  opens 
key.  There  should  be  no  movement  of  milammeter  needle 
and  no  effect  at  electrodes.  He  then  advances  the  slider 
a  short  distance,  closes  the  key,  saying  "close,"  then  as 
soon  as  the  milammeter  reading  can  be  made,  opens 
the  key  and  says  "open."  Experimenter  must  watch  mil- 
ammeter, leaving  subject  to  report  effects.  If  the  current 
is  allowed  to  flow  too  long  there  are  changes  in  irritability 
which  destroy  the  value  of  the  results.  Advance  slider 
again  and  stimulate  again.  Continue  in  this  way,  trying 
to  find  the  least  current  that  will  give  the  effects  mentioned 
in  the  table.  Of  course  the  experiment  must  stop  when  the 
stimulus  causes  too  much  discomfort.  KOC  is  usually  not 
obtained  for  this  reason.  No  graphic  record  is  taken. 
When  table  is  completed,  return  slider  to  place  of  starting, 
rock  the  commutator,  to  reverse  the  current,  then  stimulate 
with  various  strengths  of  current  as  before.  Observe  that 
the  order  of  appearance  of  KCC,  ACC,  AOC,  KOC,  are 
the  same  as  before,  but  that  they  appear  at  the  opposite 
hand.  Do  not  take  time  to  read  milammeter  in  the  second 
test.  Table  is  to  be  made  out  for  each  student,  and  each 
reports  results  obtained  by  the  experiment  on  himself. 


94  KXl'F.RIMENT  XVni. 


RESPONSE  OF  HUMAN  NERV'ISS  TO  DIRECT  CURRENT.  95 


gS  ■  EXPERIMENT  VIII. 


EI^P'ECT  OF  CURRENT  ON   IRRITABILITY  OF  NERVES.         97 


EXPERIMENT  XIX. 

The  Influence  of  the  Direct  Current  on  the  IrritabiHty 
of  Human  Nerves. 

The  plan  of  this  experiment  is  to  stimulate  the  nerves 
with  induction  shocks,  and  then,  while  the  excitation  con- 
tinues, to  introduce  the  direct  current  at  the  same  electrodes 
and  observe  the  effect  of  the  latter  upon  the  sensory  and 
motor  effects  of  the  excitation. 


Fig.  24.  Apparatus  for  testing  tlie  effect  of  a  direct  current  on  the  irritability 
of  human  nerves.  G,  key;  F,  post  where  current  enters,  and  N,  where  it  leaves 
the  rheostadt;  PP,  post  connected  with  the  slider,  from  which  current  goes  to 
mllammeter;  H,  slider;  I,  milammeter;  J,  commutator;  K,  electrodes;  NN,pole 
on  rheostadt  connected  with  N,  and  receiving  current  returning  from  commu- 
tator; X,,  secondary  coil  of  induction  apparatus;  M,  primarj'  coil;  O,  key;  Q, 
dr5'  cell. 

Apparatus. — Use  the  apparatus  employed  in  Experi- 
ment XVIII,  and  in  addition  connect  battery  and  key  with 
the  automatic  interrupter  of  the  induction  coil,  and  connect 
the  secondary  coil  with  commutator  and  one  of  the  elec- 
trodes as  shown  in  Fig.  24.  X^otice  that  the  induced  cur- 
rent will  pass  through  commutator,  milammeter,  and  rheo- 
stadt and  that  the  direct  current  will  pass  through  the 
secondary  coil.  In  other  words,  the  direct  and  induced 
currents  will  flow  at  the  same  time  through  rheostadt,  mil- 
ammeter,  commutator,   secondary   coil   and  electrodes. 


98  EXPERIMENT   XIX. 

Students  are  apt  to  become  confused  in  this  experiment 
because  two  electric  currents  are  used,  getting  the  impres- 
sion that  the  two  currents  in  some  way  neutralize  each  other 
in  traversing  the  same  path.  This  is  not  the  case.  The 
changes  observed  in  the  response  of  the  nerves  and  muscles 
to  the  induction  shocks  when  the  direct  current  is  passing 
are  due  to  changes  in  irritability  of  the  nerves  caused  by 
the  direct  current,  the  anode  of  the  direct  current  lessening 
and  the  kathode  increasing  the  irritability  of  the  nerve. 
The  tetanizing  induced  current  is  used  simply  as  a  means  of 
exciting  the  nerve  a  definite  amount.  Like  results  arc- 
obtained  if  the  nerve  be  excited  by  a  mechanical  stimulus, 
as  a  blow  from  a  light  hammer. 

Experiment. — Wet  arms  and  electrodes;  place  the  lat- 
ter over  nerves,  using  the  same  motor  points  as  in  the  last 
experiment,  and  fasten ;  see  that  slider  touches  flat  side  of 
checking  post ;  then  close  key  G  and  see  that  no  current 
passes  the  milammeter.  Now  proceed  as  in  Experiment 
XVIII  until  a  position  of  the  slider  is  found  giving  a  direct 
current  sufficient  to  cause  a  kathodic  closing  sensation  but 
no  contraction.  With  slider  in  this  position  and  key  G 
open,  find  position  of  secondary  coil  such  that  a  tetanizing 
current  will  provoke  a  small  contraction.  Observe  which 
is  the  more  active  pole,  and  rock  the  commutator  so 
that  anode  of  the  direct  current  will  be  brought  to  that 
pole.  With  the  apparatus  as  now  placed,  the  influence 
of  the  direct  current  can  be  observed  in  two  places,  where 
anode  is  applied  at  more  active  pole,  and  where  kathode  is 
applied  at  less  actii'e  pole. 

Close  key  0  and  start  the  vibrator.  When  the  con- 
traction produced  has  continued  about  5  seconds,  close 
ke}'  G  and  thus  introduce  a  weak  direct  current.  Observe 
lhe  effect  at  each  pole,  as  regards  the  sensation  and  the 
contraction  due  to  the  induction  shocks.  The  effect  of  the 
anode  of  the  direct  current  to  lessen  irritability  should  be 
more  marked  than  the  effect  of  the  kathode  to  increase  it. 
Leave  the  direct  current  flowing  for  5  seconds,  then  open 
key  G  and  notice  the  after  eft'ects,  especially  at  the  pole 
at  which  the  anode  has  been  acting.     As  soon  as  the  after 


EFFECT  OF  CURRENT  ON    IRRITABILITY   OF   NERVES.         99 

effects  have  been  observed,  open  key  0  to  stop  the  excita- 
tion, and  wait  5  minutes  for  the  effects  to  pass  oft". 

Rock  the  commutator,  reversing  the  direct  current,  and 
study  in  the  same  manner  the  other  case :  kathode  applied 
at  more  actirc  pole  and  anode  at  less  aetk'e  pole. 

The  experiment  is  to  be  performed  upon  each  student, 
each  writing  in  his  notes  the  effects  observed  on  himself. 


lOO. 


EXPKRIMF.NT   XIX. 


KFFECT  OF   CURRENT  ON    IRRITACIEITY  OE  NERVES.       I  CI 


EXPERIMENT    XIX. 


CURRENTS  OF  REST   AND   ACTION.  IO3 

EXPERBIEXT  XX. 

Currents  of  Rest  and  Currents  of  Action. 

a.  Cur  rent   of   Rest   defected    by   Rlicosco[^ic   Frog   Prep- 

aration. 

Apparatus. — ]\Iount  on  short  stand  a  brass  L  rod,  and 
fasten  a  muscle  clamp,  with  the  jaws  horizontal,  to  the 
short  arm  of  the  rod.  Connect  a  dry  cell  and  a  key  with 
an  induction  apparatus  so  as -to  give  tetanizing  excitations, 
and  connect  a  pair  of  copper  electrodes  with  the  secondary 
coil. 

Experiment. — Prepare  (A)  a  nerve-muscle  preparation, 
(B)  a  nerve-leg  preparation  (a  rheoscopic  frog  prepar- 
ation), and  (C)  a  piece  of  thigh  muscle  having  one  unin- 
jured surface  and  one  surface  cut  squarely  across  the 
fibers.  To  prevent  drying,  put  between  layers  of  filter  paper 
moistened  with  physiological  salt  solution.  Place  knee 
joint  of  B  in  clamp  with  leg  pointing  upward  and  nerve 
hanging;  below.  Avoid  clamping  the  nerve.  Place  C  on 
a  glass  slide ;  make  a  fresh  cross  section  on  C ;  then  hold- 
ing glass  slide  in  hand,  bring  C  up  beneath  B  in  such 
a  wav  that  the  nerve  of  B  shall  fall  suddenly  across  cut 
surface  and  normal  surface  of  C.  B  should  contract, 
because  the  injured  part  of  the  muscle  C  is  undergoing 
katabolic  change  and  is  consequently  negative  as  compared 
with  the  normal  surface.  The  nerve  closes  the  circuit  and 
is  stimulated  by  the  so-called  "Current  of  rest,"  the  "De- 
marcation current." 

b.  Current  of  Action  detected  by  Rheoscopic  Frog  Prep- 

aration. 

Mount  the  glass  side  in  holder  on  L  rod,  and  the  rod 
on  a  stand.  Place  A  upon  the  slide,  and  clamp  the  L  rod 
so  that  the  nerve  of  B  lies  lengthwise  upon  the  muscle  of  A. 
Stimulate  nerve  of  A  with  tetanizing  current  of  medium 
streno-th.     Both  muscles  should  be  tetanized. 


I04  EXPERIMENT  XX. 

To  find  if  currents  spreading'  from  electrodes  have 
caused  B  to  contract,  ligature  nerve  of  A  tightly  at  its 
middle,  with  a  moist  ligature,  and  then  stimulate  above 
ligature.  Xo  contraction  of  A  or  B  occurs.  The  ligature 
would  not  block  an  electric  current,  but  by  breaking  the 
continuity  of  the  nerve  fibers,  it  efifectually  blocks  a  nerve 
impulse.  It  follows  that  B  must  have  been  stimulated  by 
the  "Current  of  action"  the  "Negative  variation  Current," 
of  the  muscle  A.  When  A  contracts,  a  wave  of  con- 
traction passes  over  it,  and  at  a  given  instant,  some  parts 
are  undergoing  greater  katabolic  change  than  others, 
and  hence  are  electrically  negative  as  compared  with  the 
less  active  parts.  The  nerve  completes  the  circuit  and  is 
stimulated.  Put  preparation  A  and  B  in  moist  filter  paper, 
to  be  used  in  demonstration  to  follow,  in  which  the  currents 
of  rest  and  action  of  muscle,  nerve  and  heart  are  detected 
with  the  aid  of  a  galvanometer  and  a  capillary  electrometer. 


CURRENTS  or"  REST  AND  ACTION.  105 


Io6  EXPERIMENT  XX. 


THE  REFLEX  FROG.  I07 

EXPERIMENT  XXL 

The  Reflex  Frog. 

The  value  of  this  experiment  is  great  if  it  be  properly 
interpreted.  Through  it  we  have  the  best  physiological 
evidence  of  the  method  of  spread  of  reflex  processes  in  the 
spinal  cord.  When  stud}'ing  the  movements  which  result 
from  excitation,  one  should  try  to  recall  the  finer  anatomy 
of  the  spinal  cord,  the  longitudinal  paths  of  conduction,  the 
method  of  communication  between  the  posterior  and  anter- 
ior roots,  and  the  way  impulses  pass  from  side  to  side  of 
the  cord. 

a.     Time  of  Recovery  from  Shock. 

Pith  a  frog's  brain  and  plug  cavity  of  skull  with  as  little 
loss  of  blood  as  possible.  N^ote  the  time  at  which  this  is 
done.  Place  the  frog  on  a  plate,  back  upwards,  and  with 
the  legs  stretched  out  at  full  length,  note  the  time  required 
for  recovery  from  the  shock,  as  shown  by  the  drawing 
up  of  the  legs.  Xow  cover  with  moist  paper  and  leave 
for  half  an  hour.  At  the  end  of  this  time  observe  the 
frog's  position.  If  cerebrum  and  cerebellum  have  been 
completely  destroyed,  it  will  lie  with  nose  against  plate  ;  if 
turned  on  back  it  will  not  turn  over ;  if  thrown  in  water  it 
will  not  try  to  swim  ;  if  stimulated  it  will  move  legs  but  not 
jump;  the  power  to  perform  highly  coordinated  movements 
is  absent. 

h.     Spread  of  Reflexes. 

Clamp  nickled  L  rod  on  stand,  and  put  frog-hook  on 
short  arm  of  L.  Suspend  the  frog  from  hook  passed 
through  nose.  Gently  irritate  flank  with  a  needle  and  ob- 
serve local  twitching  of  muscles  :  excite  more  strongly  and 
notice  spread  of  reflexes  to  limbs.  Pinch  a  toe  gently  and 
then  more  strongly  (do  not  crush)  and  observe  and  note  the 


I08  EXPERIMENT  XXI. 

order  in  which  the  different  parts  of  the  leg  and  of  the  body 
respond  to  the  excitation. 

c.  Are  Reflexes  Purposeful? 

Place  beneath  frog  a  battery  jar  two-thirds  full  of  water, 
so  that  by  lifting  the  jar  the  body  can  be  washed.  Caution. 
— In  this  and  the  following  tests  requiring  the  use  of  acid, 
be  sure  to  wash  it  off  after  each  test.  Put  a  bit  of 
paper  i  mm.  square,  wet  in  io%  acetic  acid  on  right  flank, 
left  flank,  median  line  of  lower  back,  and  on  various  parts 
of  leg,  and  state  in  your  notes  the  results.  Hold  right  foot 
lightly  and  put  paper  on  the  right  flank.  Reflex  should 
appear  in  right  leg,  and  later  in  the  left  leg.  The  word 
purposeful  in  the  question  heading  this  section  is  not  used 
in  the  sense  of  well  adapted  to  the  needs  of  the  animal,  but 
directed  by  volition  to  accomplish  a  definite  object.  In 
short,  do  the  movements  of  the  frog  justify  the  view  that 
the  spinal  cord  is  the  seat  of  intelligence? 

d.  Reflex  Time. 

Immerse  tip  of  longest  toe  in  o.i%  H^SO^  up  to  a 
definite  mark,  noting  number  of  seconds  between  immersion 
and  withdrawal.  Repeat  five  times  with  each  foot  and 
report  average  for  each.  Immerse  to  the  same  mark  each 
time,  as  the  distance  affected  influences  the  result.  Wash 
off  acid  after  each  test.  Where  is  the  time  yrobably  lost? 
Does  the  experiment  favor  the  "neurone  theory,"  or  the 
theory  of  a  continuous  nervous  network  ? 

e.  Spasm  of  Muscles  -t'crsus  Coordinated  Mo-vements. 

Ai'TARATus. — Arrange  induction  coil  to  give  tetanizing 
excitations.  Connect  a  pair  of  copper  electrodes  with  the 
secondary  coil. 

ExPEKiMENT.— Remove  frog  from  hook.  Open  abdo- 
men by  cutting  away  whole  of  anterior  wall ;  remove  vicera 
without  injuring  the  sciatic  plexuses  behind  them.  When 
the  flow  of  blood  has  ceased,  cut  through  the  middle  of 
the  sciatic  plexus  on  one  side,  and  free  the  nerves  so  that 
they  can  be  laid  across  a  pair  of  electrodes.     Put  frog  on 


THE  REFLEX  FROG.  109 

hook.  Appl}^  electrodes  first  to  the  peripheral,  and  after, 
to  the  central  cut  ends  of  the  nerves  of  the  plexus,  taking 
care  to  use  the  weakest  effective  tetanizing  current  and  to 
avoid  touching  the  electrodes  to  anything  except  the  nerves. 
Explain   how   the   resulting  movements    differ? 


no 


F,XPERIM(;NT  XXI. 


THK  RKFtEX  FROG.  m 


EXPERIMENT   XXI. 


RCACTIOX    TIME   TO   SOUND. 


113 


EXPERIMENT  XXII. 


Reaction  Time  to  Sound. 


Apparatus. — Blacken  drum  and  fasten  it  at  highest 
point  on  kymograph.  Arrange  to  turn  it  by  hand.  Fasten 
the  heavier  muscle  lever,  with  supporting  screw  down,  on 
long  stand  at  such  height  that  it  will  write  2  cm.  from 
bottom  of  drum.  Put  L  rod  on  stand  above  lever ;  put 
elastic  band  on  rod ;  and  connect  band  with  lever  l^y  a 
thread  put  through  second  hole,  so  that  band  will  be  slightly 
stretched.  Fasten  one  end  of  a  thread  to  the  strip  of  wood 
provided,  by  passing  thread  through  hole  nearest  the  end 
and  back  through  other  hole,  and  tieing  it  so  that  thread 
will  not  slip.  Fasten  other  end  of  thread  to  third  hole  in 
lever,  leaving  thread  of  such  length  that  the  end  of  the 
piece  of  wood  to  which  thread  is  fastened  will  be  so  near 
the  table  that  when  it  is  pressed  on  by  finger  the  lever 
will  move  about  4  mm.  Bring  writing  point  of  lever  to 
dirum.  Mount  fork  on  short  stand,  and  place  this  stand 
so  that  fork  will  write  the  time  one  centimeter  below  lever 

and  in  same  vertical  line. 

Experiment. — The  subject 
is  to  put  finger  on  strip  of  wood 
and  depress  it  bo  that  the  lever 
is  pulled  down  and  the  wood 
rests  on  table ;  ( see  that  the 
thread  is  veriical).  He  is  to 
remove  finger  as  soon  as  he  can 
after  hearing  sound  of  fork.  He 
nmst  not  react  to  soimd  of  the 
moving  drum,  and  to  give  quick 
response  must  have  in  mind  the 
sound  of  fork.  The  experi- 
menter must  put  yoke  on  fork  ; 
tell  subject  to  close  eyes:  say 
"ready,"  and  about  a  second 
later  whirl  the  drum  ;  then  pull  yoke  off  fork  and  stop  drum 
as  soon  as  subject  is  seen  to  respond. 


•v: 


s^ 


Kig.  25.  Apparatus  for  record- 
ing reaction  time  for  sound.  A. 
rubber  baud;  B,  lever;  C,  tuning 
fork;  D,  strip  of  wood,  which  is 
to  be  pressed  by  finger  against 
table. 


114  EXPERIMENT  XXII. 

Rehearse  the  experiment  two  or  three  times  without 
the  pointers  touching  the  drum.  Then  move  drum  up  to 
pointers  and  see  that  they  write  well.  Mark  the  relative 
position  of  the  pointers  on  the  drum  by  moving  them.  If 
the  kymograph  or  either  stand  is  moved  at  any  time,  the 
relative  position  of  the  writing  points  must  be  again  marked. 
Do  not  fail  to  mount  part  of  curve  showing  the  position  of 
writing  points  along  with  the  rest.  Take  lo  reaction  times 
with  each  student  as  subject,  moving  drum  down  after  each 
experiment. 

Reading  of  Curves. — Draw  perpendicular  with.,  triangle 
from  point  where  lever  began  to  move,  through  the  cor- 
responding tuning-fork  curve.  Count  the  number  of  waves, 
starting  with  the  crest  of  the  first  and  estimating  in  tenths 
the  value  of  any  fraction  of  a  wave  at  the  end.  State  time 
in  hundredths  of  a  second.  Give  in  notes  result  of  the 
separate  observations  and  the  average  of  lo  observations. 
Throw  out  only  such  observations  as  were  known  to  be 
faulty  at  the  time  they  were  made.     Account  for  variations. 

Ordinary  reaction  time  to  sound  is  0.15 — 0.20  second; 
to  a  tovich  on  the  skin,  0.145  second;  and  to  an  electric 
flash  0.195  second. 


RKACTION   TiMIi;   TO   SOUND. 


115 


ii5 


j:;XPr;Ri.Mi:NT  xxti. 


Tilt;   KXICK-JERK. 


117 


EXPERIMENT  XXIII. 


The  Knee-jerk  as  Modified  by  Reenforcing  and  Inhibit- 
ing Influences. 

If  a  blow  be  struck  on  the  ligamentum  patellae  when  the 
lower  leg"  is  in  a  position  that  puts  the  ligament  under  slight 


Kig.  26.  Diagram  of  nervous  patlis  followed  by  the  nerve  impulses  causing 
the  knee-jerk  and  its  reenforcemeuts.  A,  hammer  placed  to  strike  ligamentum 
patellse;  B,  quadriceps  muscle;  C,  posterior  spinal  nerve  root;  D,  motor  cell  in 
anterior  horn  of  gray  matter  of  lumbar  cord;  E,  anterior  spinal  nerve  root  ;F, 
sensory  nerve  from  other  leg;  G,  comniisural  cell;  H,  descending  path  from  leg 
area  in  cerebral  cautex;  I,  descemling  path  from  arm  area  in  cerebral  cautcx; 
J,  motor  nerve  to  arm. 


ii8 


EXPEKIMENT  XXIII. 


tension,  a  sudden  twitch  is  transmitted  to  the  vastus  internus 
and  crureus  divisions  of  the  quadriceps  extensor  muscle. 
The  result  is  a  sudden  contraction  of  these  muscles  and  a 
sudden   forward  swing  of  the  leg. 

Two  explanations  of  the  sudden  contraction  of  the 
muscle  are  offered;  viz:  (i)  The  knee-jerk  is  a  reflex 
act.  The  twitch  acts  as  a  mechanical  stimulus  to  the  sen- 
sory nerve  ends  in  the  muscle  and  its  tendon,  and  causes 
a  reflex  contraction  of  the  muscle,  which  causes  the   foot 


Kig.  27.  Method  of  supporting  thigh  and  foot  and  of  recording  the  swing  of 
the  lower  leg  in  the  knee-jerk  experiment.  A,  support  under  thigh;  B,  pulley; 
C,  cross  shape<l  writing  needle;  D,  rubber  band,  twisted  so  as  to  keep  point  of 


ipe<l  writing 
needle  against  drum;  E,  knee-jerk  hammer 


to  swing  if  it  is  free  to  move.  The  anterior  horn  cells  taking 
part  in  this  act  are  in  the  leg  areas  of  the  third  and  fourth 
lumbar  segments  of  the  cord.  The  response  of  these  cells 
to  the  sensory  stimulus  from  the  extensor  muscles,  is  either 
reen forced  or  inhibited  by  other  impulses  reaching  the 
anterior  horn  cells  a  short  time  before  the  impulses  from 
the  leg.  (2)  The  knee-ierk  is  the  result  of  the  direct 
mechanical  stimulation  of  the  muscle.  The  greater  the 
tension  the  better  the  muscle  responds  to  the  blow  on  the 
tendon.     The  anterior  horn  cells  are  always  during  waking 


THE  KNEE-JERK.  I  1 9 

hours  sending  tonus  impulses  to  the  muscles  which  keep 
them  under  more  or  less  tension,  and  these  impulses  are 
increased  bv  reenforcing  and  decreased  by  inhibiting  in- 
fluences. It  will  be  here  assumed  that  the  former  explana- 
^tion  is  correct. 

Appakatus  and  Position  oe  Subject. — The  subject  is 
to  lie  on  his  left  side  with  his  head  on  a  pillow,  his  thigh 
on  a  support,  and  his  foot  in  a  swing.  The  position  must 
be  perfectly  comfortable,  so  that  he  could  go  to  sleep. 
Adjust  the  support  (A)  tmder  the  thigh  so  that  the  lower 
leg  will  swing  freely.  The  subject  must  be  in  such  a  posi- 
tion that  the  cord  suspending  the  swing  is  vertical  when 
the  leg  is  at  rest ;  and  throughout  the  work  he  must  lie 
quietly  and  relaxed  with  eyes  closed  except  when  told  to 
do  otherwise.  Connect  the  back  of  the  swing  by  thread 
passing  round  pulley  (B)  to  a  cross  shaped  writing  needle 
(C),  so  that  the  rubber  band  (D)  supporting  the  latter  is 
under  a  slight  tension  and  the  needle  free  to  move.  Adjust 
the  hammer  (£)  so  that  when  it  hangs  vertically,  the  mid- 
dle of  the  striking  face  will  just  touch  the  skin  over  the 
middle  of  the  ligamentum  patellae,  and  so  that  the  blow 
will  be  struck  at  riglit  angles  to  the  ligament.  Make  this 
adjiistiiieiit  with  great  care,  then  clamp  the  rod  supporting 
the  hammer. 

Experiment. — Four  students  work  together,  each  taking 
his  turn  as  subject,  experimenter,  assistant,  and  clerk.  The 
experimenter  uses  the  hammer  ;  the  assistant  sits  near  the 
head  of  the  subject  and  applies  the  sensory  or  psychic 
stimuli  when  signaled  by  the  experimenter ;  the  clerk  looks 
after  the  drum,  and  keeps  record  of  any  reenforcing  or 
inhibiting  stimuli,  marking  on  the  drum,  i,  2,  3,  etc.,  to  cor- 
respond to  his  notes.  During  the  entire  experiment  the 
subject  must  be  completely  relaxed  and  the  room  perfectly 
quiet.  Success  depends  entirely  on  the  contrast  between 
repose  and  action  of  the  central  nervous  system.  If  those 
who  make  the  experiment  are  not  quiet  and  annoy  or  excite 
the  subject,  except  when  a  special  efifect  is  desired,  the 
whole  experiment  fails. 


I20  EXPERIMENT  XXIII. 

a.  Minimal  Blow  Xcccssary  to  Excite. 

Adjust  arm  supporting  catch  for  hammer  so  that  index 
points  at  io°  ;  put  hammer  on  catch,  release  hammer  and  let 
it  strike  the  tendon,  catching  it  as  it  rebounds,  so  that  a 
second  blow  shall  not  be  struck.  Turn  drum  5  mm.  and 
continue,  raising  and  lowering  arm  supporting  hammer 
until  the  least  blow  is  found  which  will  cause  a  knee-jerk. 
Make  note  of  the  position  of  hammer  for  this  minimal  blow. 

b.  Record  of  Normal  Knee-jerk. 

Find  position  of  hammer  that  will  give  a  knee-jerk 
whose  record  on  drum  is  about  2  cm.  high.  Make  note  of 
position  of  hammer.  Start  drum  at  2  or  3  mm.  per  second 
and  record  a  series  of  20  normal  knee-jerks,  giving  the 
blows  rythmically  at  such  a  rate  that  the  foot  has  time  to 
come  to  rest  after  each  jerk.  Observe  that  even  when  sub- 
ject is  relaxed  and  the  room  quiet,  the  knee-jerks  vary  in 
height,  in  other  words,  that  the  irritability  of  the  reflex 
mechanisms  is  changing. 

c.  Motor  Recnforcement. 

Let  the  subject  clench  his  hand  at  the  instant  a  com- 
mand is  given  him,  the  hammer  being  released  at  varying 
intervals.  If  the  blow  on  the  knee  occurs  at  the  exact 
instant  the  command  to  clench  is  given,  or  within  0.4  second 
after  the  command,  the  knee-jerk  is  gi"eater  than  normal, 
i.  e.,  reenforced,  if  the  blow  is  struck  between  0.4  and  1.7 
seconds  after  the  command,  the  response  is  lessened,  i.  e., 
inhibited.  If  the  blow  comes  still  later,  the  clench  has  no 
effect.  Record  10  or  more  normal  responses,  and  when 
they  are  of  about  the  same  height,  try  the  effect  of  clench- 
ing, the  clerk  making  a  mark  on  drum  to  indicate  the  jerks 
with  which  a  clench  was  given,  then  record  another  series 
of  normal  jerks.  The  explanation  of  the  effect  of  the 
clench  is  that  when  the  motor  cells  of  the  arm  area  of  the 
cerebral  cortex  act,  the  motor  cells  of  the  leg  area  of  the 
cerebral  cortex  are  excited  through  association  fibers,  and 
im]5ulses  from  the  cells  of  the  leg  area  of  the  cortex  spread 
to  the  anterior  horn  cells  of  the  leg  area  of  the  cord.     If  the 


THE  KNEE-JERK.  121 

impulses  coming  from  the  brain  reach  the  lumbar  region 
of  the  cord  before  the  sensory  impulses  from  the  leg,  they 
so  alter  the  condition  of  the  anterior  horn  cells  that  the 
reflex  response  to  the  blow  is  altered.  Sudden  discharge 
of  voluntary  impulses  to  any  other  muscles,  e.  g.,  clenching 
the  jaw,  or  even  winking,  will  also  cause  a  reenforcement 
or  inhibition. 

d. — Reenforcement  by  Sensory  Stimuli. 

Pulling  a  hair,  tickling  face  with  a  camel's  hair  brush, 
an  unexpected  sound  or  odor,  will  cause  a  reenforcement. 
To  show  this,  record  lo  or  more  normal  jerks  by  a  series  of 
rhythmical  strokes,  and  when  the  jerks  are  of  about  equal 
height,  test  several  sensory  effects,  marking  on  drum  the 
time  such  stimuli  are  given. 

e.     Psyehic  Recnforeemcnt. 

With  subject  as  quiet  as  possible,  eyes  closed,  room  per- 
fectly still,  record  a  series  of  lo  or  more  normal  jerks,  and 
while  the  record  is  being  taken,  test  the  effect  ( i )  of  speak- 
ing to  subject.  (2)  of  asking  him  to  multiply  two  numbers 
given  him,  (3)  let  him  think  of  some  stirring  poem,  etc. 
The  clerk  should  note  all  these  occurrences  with  care,  and 
also  the  eft'ect  of  sounds  produced  in  neighboring  rooms  or 
out  of  doors,  the  entrance  of  any  one  into  the  room,  -and  all 
external  influences  that  are  able  to  excite  the  subject  in 
the  least  degree.  The  susceptibility  to  such  influences 
varies  greatly  with  the  subject.  The  student  who  was  the 
subject  of  the  experiment,  is  to  have  the  record. 


122  EXPERIMENT  XXIII. 


THE  KNEK-JERK.  1 23 


124 


EXPERIMENT  XXni. 


CONDITIONS  DETERMINING  BLOOD  PRESSURE. 


EXPERIMENT  XXIV. 

Conditions    Determining    the    Blood    Pressure,    and    the 
Output  of  the  Ventricle. 

porter's    artificial    CIRCULATION    APPARATUS. 

The  basin  supplying  and  receiving  the  water  represents 
the  left  auricle.  The  bulb  which  pumps  the  water  represents 
the  left  ventricle.  The  valves  at  the  inlet  and  outlet  of  the 
bulb  represent  the  mitral  and  aortic  valves.  The  piece  of 
ratan  and  the  side  tube  controlled  by  clamp  represent  the 
capillaries  and  the  variable  resistance  of  the  small  arteries. 
The  tubes  between  the  aortic  valve  and  the  resistance  repre- 
sent the  arteries.  The  tubes  between  the  resistance  and 
the  basin  represent  the  veins.  Two  manometers  connected 
with  arteries  and  veins  permit  a  study  of  pressures  under 
varying  conditions.  A  tube  connects  the  ventricle  with  a 
tambour,  b}'  means  of  which  changes  in  pressure  in  the 
ventricle  can  be  observed.  A  tambour  can  be  placed  over 
the  artery  and  enables  the  pulse  to  be  recorded. 

Make  a  diagram  showing  these  various  parts  of  the 
apparatus.  After  making  the  diagram,  see  that  the  clamp 
on  the  side  tube  is  open  and  then  fill  the  tubes  with  water, 
b\-  pumping  while  holding  the  right  hand  end  of  the  appar- 
atus up  at  an  angle  of  45'.  Always  pump  b}'  compressing 
the  bulb  quickly  and  instantly  removing  the  pressure,  re- 
peating rhythmically  every  tivo  seconds.  Compress  the 
bulb  only  by  means  of  the  lever  placed  above  it,  and  see 
that  the  rod  limiting  the  movement  of  the  lever  is  in  its 
clamp,  with  the  longer  end  upward.  Using  the  apparatus 
in  this  way,  prepare  to  demonstrate  to  the  instructor  the 
points  enumerated  below  before  proceeding  to  the  second 
])art  of  the  experiment. 


126  EXPERIMENT  XXIV. 


PART    I. 


I. — The  fluid  takes  path  of  least  resistance,  nearly  all 
of  it  going-  through  the  open  side  tube  and  but  little  through 
the  ratan. 

2. — Only  a  part  of  the  fluid  pumped  escapes  into  the 
basin  during  systole. 

3. — The  part  held  back  dilates  the  arteries  and  escapes 
during  diastole. 

4. — The  part  of  the  artery  nearest  the  heart  expands  first. 

5. — Finger  placed  on  ventricle  tambour  feels  a  sudden 
rise  of  pressure  followed  by  a  sudden  fall  of  pressure. 

6. — Arterial  manometer  shows  rise  of  pressure  later 
than  ventricle  tamborrr. 

7. — The  meixui'v  oscillates  after  each  beat.  l:)ecause  of 
its  own  inertia. 

(7.     Effect  of  Chauii^ini!:^  Peripheral  Resistance. 

^^'ithout  changing  the  rate  or  manner  of  pumping,  grad- 
ually increase  the  peripheral  resistance  by  slowly  screwing 
up  the  pressirre  clamp  on  side  tube;  observe,  i. — Increase 
of  arterial  pi"essure,  indicated  by  arterial  manometer,  and 
visible  changes  in  size  of  arteries ;  also  decrease  of  venous 
pressure  indicated  by  venous  manometer.  2. — Decrease  of 
outflow,  indicated  by  the  size  and  character  of  the  stream 
flowing  into  the  basin  from  veins.  3. — Increased  work  for 
heart  as   felt  by  the  hand  and  ventricle  tambour. 

Caution. — Keep  watch  of  the  manometer  as  the  clamp 
is  closed,  and  avoid  forcing  the  mercury  out  of  the  tube. 

b.     Effect  of  Chaiii:;i)ig  Rate  of  Heart  Beat. 

With  clamp  on  side  tube  open  wide,  ( small  peripheral 
resistance)  observe  the  following:  i. — Slow  rate,  (once 
in  3  sec).  The  fluid  escapes  into  the  basin  completely  dur- 
ing the  diastole.  (The  flow  is  intermittent.)  2. — Medium 
rate,  (once  in  i  sec).  The  fluid  pum])ed  does  not  all 
escape  into  the  basin  during  diastole.  (The  flow  is  remit- 
tant.       3. — Fast    rate,     (three    times    per    sec).       Marked 


CONDITIONS  DETERMINING  BLOOD  PRESSURE.  I  27 

accumulation  of  fluid  in  the  arteries  causing  distension 
of  walls,  and  continuous  outflow  approaching-  constancy. 
The  energy  stored  in  the  walls  of  the  elastic  arteries  during 
systole  drives  the  fluid  on  during  diastole.  The  pressure, 
as  shown  by  manometers,  is  never  high  when  side  tube  is 
open,  no  matter  how  rapid  the  beat. 

c.  Effect  of  Changing  flic  J^ohnuc  Pumped  per  Beat. 

Remove  the  rod  limiting  the  pressure  of  lever  on  bulb, 
and  replace  it  with  its  shorter  end  upward,  and  observe  the 
efifect  on  the  pressure  and  the  outflow,  pumping  at  rate  of 
once  in  two  seconds.  Demonstrate  above  points  to  instruc- 
tor, before  proceeding  further. 

PART    II. 

d.  Record  of  Pulse  from  the  Artificial  Circulation  Appar- 

atus. 

The  method  of  air  transmission  devised  by  Marey,  is 
employed  to  record  a  great  variety  of  physiological  move- 
ments. By  this  method,  two  little  drums  covered  with 
rubber  membrane  are  connected  together  b)^  tubing.  A 
plate  of  metal  resting  on  the  membrane  of  one  of  the  drums 
(the  recording  tambour.  Fig.  28),  is  connected  with  a  light 
lever,  and  when  air  is  driven  out  of  or  enters  the  other 
drum  (the  receiving  tambour),  by  movements  imparted  to 
the  membrane  covering  it,  the  lever  rises  or  falls.  There 
is  a  T  tube  at  one  part  of  the  tubing  connecting  the  drums, 
and  this  supplies  a  side  opening  by  which  air  can  enter 
or  escape  when  the  tambours  are  not  in  use.  This  opening 
is  controlled  by  a  pinch-cock.  The  level  of  the  lever  can 
be  adjusted  by  placing  the  support  of  its  axis  at  a  suitable 
angle. 

Caution. ^Do  not  apply  pinch-cock,  excepting  when 
the  tambours  are  to  be  used.  See  that  the  lever  of  the 
recording  tambour  is  horizontal  just  before  a  record  is  to 
be  taken,  and  never  let  the  membrane  of  the  recording  tam- 
bour be  greatly  stretched. 

Adjust  a  receiving  tambour  to  wall  of  artery,  and  con- 

10 


I2J 


EXPERIAIENT  XXIV. 


nect  it  to  a  recording  tambour.     Clamp  the  tube  leading  to 
arterial  manometer.     Replace  rod  limiting  pressure  of  lever 

on  bulb,  with  its  longer 
c        .  end     upward ;     then 

pump  in  the  manner 
directed  at  the  rate  of 
once    in    two   seconds. 

i'lg.  28.     Recording   tambour.      A,    tambour;  ... 

B,  aluminum  plate,  with  bell-and-socket  joint  No    pulsC    IS    glVCll  With 

for  pin  acting  on  lever;   C,  lever  with  celluloid  .  ,             , 

writing  point;  D,  support  of  lever.  Side    tubC,     representing 

small  arteries,  wide 
open.  Gradually  increase  the  peripheral  resistance,  and 
observe  the  resulting  distension  of  large  artery  and  pulsa- 
tion of  tambour.  Several  beats  will  be  required  to  fill  the 
artery  before  the  tambour  will  respond.  Record  on  drum. 
By  careful  adjustment  of  peripheral  resistance  and  regular 
and  uniform  pumping,  a  pulse  can  be  recorded  that  is  a 
fair  imitation  of  a  normal  pulse  curve  from  man.  Record 
curves  as  follows : 

I. — Imitate  a  normal  pulse,  and  dicrotic  pulse,  i.  e.,  the 
pulse  which  comes  with  a  low  arterial  pressure. 

2. — Effect  of  slight 
A    B    c  changes    in    peripheral 

resistance.    Record  ten 

or  more  normal  beats ; 

then  make  a  slight  in- 

Fig.  29.  Sphygmogram  of  a  normal  pulse  CrcaSC  HI  the  rCSlStaUCC 
and  a  dicrotic  pulse.  A,  crest  of  primary  ^^^^  j^^rk  OU  drUm  the 
wave;  B,  dicrotic  notch;  C,  dicrotic  wave. 

time  of  the  change ; 
after  ten  or  more  beats  with  this  resistance,  return  to  the 
normal,  again  marking  on  drum. 

In  a  similar  manner  make  a  curve  showing  effect  of 
decrease  of  pressure. 

3. — Effect  of  changing  rate  of  beat.  Record  curves 
with  the  following  rates  of  beat :  I  in  2  seconds,  i  in  3  sec- 
onds, I  in  I  second.  2  in  i  second,  3  in  i  second.  In  each 
instance  the  curve  should  show  the  effect  of  changing  the 
rate. 

4. — Effect  of  changing  the  volume  pumped  per  beat. 
Show  effect  of  increasing  and  of  decreasing  the  volume  per 


CONDITIONS  DETERMINING  BLOOD  PRESSURE.  1 29 

beat,  always  marking  on  drum  the  time  the  change  is  made. 
Notes. — Describe  the  form  of  the  normal  pulse  wave 
which  you  obtained,  and  state  in  what  respects  the  form 
of  the  wave  is  changed  by  vaso-constriction,  vaso-dilation. 
increased  heart  rate,  and  increased  pulse  volume. 

c.     Coinparisoii  of  Arterial  and  J'enfriciilar  Pulse  Curves. 

Mount  a  special  tambour  on  rod  so  that  the  button  will 
rest  against  ventricle  tambour.  Record  ventricular  and 
arterial  pulses  together.  Note  difference  of  form  and  delay 
of  the  arterial  pulse. 

part   III. 

f.     Effect  of  Lesions  of  Heart  I'^alves. 

Failure  of  a  valve  to  close  its  orifice  perfectly  is  called 
insufficiency.  Abnormal  narrowing  of  its  aperture  is  called 
stenosis.  These  defects  in  the  heart  valves  are  usuallv 
accompanied  by  dilation  of  the  cavities  and  hypertrophy  of 
the  heart  muscle,  which  is  known  as  compensation.  These 
three  conditons  can  be  imitated  in  a  way  in  the  artificial 
circulation  apparatus ;  insufficiency  and  stenosis  by  the  use 
of  suitable  valves,  which  will  be  provided,  and  compensation 
by  reversing  the  rod  which  limits  compression  of  the  bulb, 
thus  permitting  greater  outflow  at  a  stroke. 

Arrange  to  record  ventricular  and  arterial  pulse  curves, 
and  then,  with  the  same  peripheral  resistan^^e  as  used  for 
imitation  of  a  normal  pulse,  and  pumping  at  the  rate  of 
once  in  two  seconds,  record  curves  to  show  effects  of  the 
following  lesions,  alone  and  with  compensations : 

I. — Aortic  Insutficleney.  The  ventricular  pulse  is  about 
normal,  but  the  arterial  pulse  shows  a  sudden  upstroke  and 
a  sudden  fall. 

2. — Aortic  stenosis.  The  ventricular  pressure  is  ab- 
normally high  and  the  arterial  pressure  is  low.  even  with 
compensation. 

3. — Mitral   Insufficiency.      Pressure  low   in   both   curves. 

4. — Mitral  stenosis.     Pressure  very  low  in  both  curves. 

Explain   the   results   in   each   case,   and   state   in    which 


130  EXPERIMENT  XXIV. 

cases  the  compensation  made  the  curve  more  nearly  normal, 
and  why. 

It  must  be  borne  in  mind  that  these  lesions  in  the  living 
subject  are  accompanied  by  other  changes,  so  that  the 
results  are  of  value  only  as  indicating  fundamental  relations, 
which  here  are  separated  from  complications  usually  present. 

Leave  apparatus  in  order  for  normal  action. 


CONDITIONS  DETERMINING  BLOOD  PRESSURE.  I^I 


132  i;xpi;rime;nt  xxiv. 


CIKCULATIOX    AND   RESPIRATION   OF    MAMMAL. 


'33 


EXPERIMENT  XXV. 


Circulation  and  Respiration  of  the  Mammal. 

Ex])erin-ients  on  these  subjects  will  fill  two  afternoons, 
the  apparatus  and  general  methods  beiiig  the  same  for  both 
da^•s.  The  students  will  work  in  groups  of  four,  and  the 
parts  of  the  work  to  be  done  by  each  student  is  shown  in 
the  follo\\ing  schedule.  The  number  of  the  student  as 
given  in  the  schedule  will  be  assigned  by  lot. 

Schedule  of  Work. 


First  Day 
Experiment  25 

Student  i 

Student  2 

Student  3 

Student  4 

Right  carotid 
and  vagus 

Operate 

Assist 

Etherize 

Apparatus 

I^eft  carotid 
and  vagns 

Apparatus 

Operate 

Assist 

Etherize 
Assist 

Sciatic 

Etherize 

Apparatus 

Operate 

Tracheotomy 
and  open  chest 

Assist 

Etherize 

Apparatus 

Operate 

Account  for 
apparatus 

Account  for 
apparatus 

Second  Day 
Experiment  26 

Right  carotid 
and  depressor 

Assist 

Etherize 

Apparatus 

Operate 

Left  carotid 
and  depressor 

Etherize 

Apparatus   '  Operate 

Assist 

Tracheotomy 
and  open  chest 

Apparatus 

Operate          Assist 

Etherize 

Phrenic  and 
peristalsis 

Operate 

Assist           '  Make  nerve 
leg  pre  part' n 

Apparatus 

Account  for 
apparatus 

Account  for 

apparatus 

Success  in  the  experiments,  recjuires  that  the  apparatus 
shall  be  thoroughly  understood  before  the  work  is  begun. 


134  EXPERIMENT   XXV. 

Students  assigned  to  this  work  will  be  given  an  opportunity 
to  study  the  apparatus,  and  be  quizzed  on  these  notes,  the 
latter  part  of  the  preceding  afternoon. 

Apparatus. — The  arrangement  of  the  apparatus  is  to 
be  seen  in  Fig.  30.  The  following  list  of  apparatus  and 
instruments  will  be  required,  and  everything  must  be  at 
hand  before  the  work  is  begun. 

Apparatus  to  be  Pnrnished  by  Laboratory. 

Animal-board  with  head-holder. 

Manometer  outfit. 

Artificial  respiration  outfit. 

Bottle  of  ether. 

Bulb  and  cannulae  for  artery. 

Cannula  for  trachea. 

Two  burette  clamps. 

Three  clamps  for  stand. 

Screw  clamp  for  trachea. 

Four  screw  clamps  for  rubber  tubing. 

Four  cords  for  animal  board. 

Two  cords  with  hooks. 

Etherizing  cone. 

Two  cloth  covers. 

Dish  for  sodium  chloride  solution. 

Dropper. 

Small  bulldog  forceps. 

Large  bulldog  forceps. 

Jar  for  sodium  sulphate. 

Battery  jar. 

Ligatures,  fine. 

Ligatures,  coarse. 

Water  manometer. 

Aneurism  needle. 

Pinch  cock. 

Rod,  nickled. 

Rubber  tube  with  glass  T. 

Scalpel. 

Sponge. 

Two  small  stands. 


CIRCULATION   AND  RESPIRATION    OF    MAMMAL. 


U5 


Receiving"  tambour. 
Recording"  tambour. 
Two  towels. 
Silk  thread  and  weight. 
Stimulating  electrodes. 
Time  signal. 

■rlpporafiis  to  be  Fiiniislied  by  tJic  Four  Students  assigned 
to  the  zvork. 

One  dry  cell. 

Induction  coil. 

Kymograph  and  two  drums. 

Mercury  key. 

Two  plates. 

Brush  for  salt  solution. 

Fine  and  strong  scissors. 

Fine  and  strong  forceps. 

Five  wires. 

Cabinet  maker's  clamp. 


Fig.  30.  Scheme  of  apparatus  for  studying  the  blood  pressure  of  a  mammal. 
A,  tambour  lever;  B,  pointer  of  a  manometer  float;  C,  time  signal;  D,  short  cir- 
cuit key;  E,  mercury  float;  F,  electrodes;  H,  bicycle  pump;  I,  anticoagulation 
fluid  pressure  bottle;  J,  manometer  communicating  with  pressure  bottle,  K, 
bulb  and  cannula;  Iv,  minimum  valve;  M,  maximum  %'alve;  i,  2,  3,  cocks;  4,  5, 
6,  clamps. 


136  EXPERIMENT   XXV. 

DIRECTIONS  TO  STUDENT  CARING  FOR  APPARATUS. 

Connect  time  signal  (C)  and  an  electric  light  switch  in 
the  clock  circuit.  Place  the  induction  apparatus  behind  the 
manometer  outfit,  and  put  a  dry  cell  and  a  key  in  the 
primary  circuit,  connecting  them  so  as  to  give  a  tetan- 
izing  current.  Connect  secondary  coil  with  shorli-circuit 
key  (D)  on  top  of  manometer  board.  Fasten  a  pair  of 
electrodes  (F)  to  key  (D),  with  wires  leading  off  in 
front  of  manometer.  Start  vibrator,  open  short  circuit  key, 
and  test  current  with  tongue.  A  current  of  medium  strength 
will  suffice.  See  that  writing  points  of  manometer  (B)  and 
key   (D)   write  in  same  vertical  line. 

Now  with  cock  i  and  clamp  5  closed,  raise  pressure  to 
90  mm.  in  bottle  (7)  containing  anticoagulation  fluid,  by 
using  bicycle  pump.  Pump  very  carefully,  or  the  mercury 
will  be  forced  out  of  manometer.  Next  raise  bulb  K,  until 
it  and  its  tube  are  vertical ;  open  clamp  6 ;  then  gradually 
open  clamp  5.  and  let  fluid  rise  in  tube  and  fill  bulb;  finallv 
close  clamp  5.  Now  lower  bulb  until  on  a  level  with  the 
mercury  of  the  recording  manometer.  Open  cock  i,  and 
as  soon  as  the  float  has  taken  its  new  position,  close  cock  i, 
and  put  bulb  in  such  a  position  that  any  drip  will  be  caught 
in  dish  provided  for  the  purpose.  Place  point  of  time 
signal  (C)  just  behind  and  on  a  level  with  the  pointer  of 
the  manometer  float  (B).  The  time  record  will  in  this 
position  give  a  base  line  from  which  all  pressures  are  to  be 
read.  Notice  that  the  mercury  in  the  two  arms  of  the 
manometer  is  not  at  the  same  level.  This  is  due  to  the 
weight  of  the  anticoagulation  fluid  on  one  side  of  the  U. 

I)y  means  of  pump,  raise  the  pressure  in  the  bottle  of 
anticoagulation  fluid  until  the  mercury  in  the  manometer 
connected  with  the  bottle  stands  at  90  mm.  Pump  with 
care.  Pinch  ofif  rubber  tube  at  opening  of  bulb ;  open  clamp 
5;  and  then  graditally  open  cock  i,  until  the  mercury  in  the 
recording  manometer  rises  to  50  mm.  Close  i  and  5.  The 
true  pressure  is  twice  the  amount  recorded,  for  the  mercury 
falls  on  one  side  of  the  tube  as  it  rises  on  the  other.  The 
object   of   raising  the  pressure,   is   to   limit   the   amount  of 


CIRCULATION   AND  RESPIRATION   OP  MAMMAL.  137 

blood  which  will  leave  the  artery  when  it  is  connected  with 
the  manometer. 

The  apparatus  must  be  ready  to  use  the  instant  that  the 
operation  is  completed.  Have  two  drums  blackened,  and 
mark  the  position  of  the  writing  points  on  the  drum  which 
is  to  be  used  first. 

During  the  taking  of  the  records  the  man  in  charge  of 
the  apparatus  must  s'art  and  stop  the  drum  ;  must  mark  the 
position  of  the  writing  points  on  the  drum  before  each 
curve  ;  must  give  the  stimulations  by  depressing  the  short 
circuit  key,  and  see  that  the  drum  runs  for  at  least  10 
seconds  before  and  15  seconds  after  each  test;  and  must 
label  each  record  with  his  name  and  the  number  of  the 
curve  before  giving  it  to  the  assistant  to  fix. 

Directions  to  Assistant. 

It  is  the  business  of  the  assistant  to  see  that  the  instru- 
ments, ligatures,  and  cannulae  are  in  order,  and  are  at  the 
hand  of  the  operator  throughout  the  operation  and  the 
experiment.  While  the  animal  is  being  etherized,  fill  the 
animal  board  with  water  at  45°  C. ;  heat  some  salt  solution 
in  a  dish  provided  for  the  purpose,  put  a  sponge  in  it,  and 
place  it  on  the  operating  table ;  also  put  two  cannulae  of 
dififerent  sizes  in  a  dish  of  anticoagulation  fluid.  During 
the  operation  be  ready  to  sponge  the  wound,  to  pass  needed 
instruments  to  the  operator,  and  to  tie  the  ligatures  when 
required.  During  the  experiment,  when  the  records  are 
being  taken,  blacken  the  drums.  There  should  always  be 
a  drum  ready  for  use. 

Anaesthesia. 

Anaesthesia  comes  on  in  three  stages :  ( i )  imperfect 
consciousness,  (2)  excitement,  (3)  complete  anaesthesia  or 
narcosis.  These  stages  show  the  following  peculiarities, 
which  must  be  kept  in  mind  in  administering  ether.  (See 
Cushny 's  Pharmacology. ) 

Stack  I. — Loss  of  consciousness  begins  toward  close. 
Struggling  because  of  dislike  of  drug ;  respiration  irregular 


138  EXPERIMENT  XXV. 

from  irritation  of  mucous  membrane,  salivation  for  same 
reason ;  pupil  dilated. 

Stage  II. — Lessening  of  reflexes  toward  end ;  struggling 
due  to  nervous  excitement  caused  by  drug ;  respiration 
heavy  with  pauses  and  gasps ;  pupil  dilated. 

Stage  III. — The  danger  period.  Unconsciousness ; 
respiration  slow  and  shallow,  often  snoring ;  pulse  slow  and 
feeble ;  pupil  small  until  danger  point  is  reached,  when  it 
dilates ;  corneal  and  other  reflexes  are  lost. 

Rabbits  differ  from  men,  dogs,  and  cats,  in  that  con- 
vulsive respirations  immediately  precede  death  in  the  third 
stage. 

Directions  to  Anaesthetizer. 

See  that  there  is  no  gas  flame  in  the  same  part  of  the 
room.  Ether  vapor  travels  far  and  is  exceedingly  inflam- 
mable. 

Let  the  student  who  is  to  operate,  hold  the  four  legs  of 
the  rabbit  between  the  fingers  of  the  left  hand,  and  hold 
the  ears  between  the  second  and  third  fingers,  and  the  nose 
between  the  thumb  and  index  finger  of  the  right  hand.  He 
should  take  care  not  to  use  unnecessary  force,  there  is  no 
need  of  hurting  the  animal. 

The  anaesthetizer  puts  some  ether  on  the  gauze  of  the 
cone,  and  places  the  cone  over  the  animal's  mouth  and 
nose.  The  ether  bottle  is  to  be  kept  corked  when  not  in 
use.  It  is  well  to  place  a  towel  beneath  the  head,  and  bring 
it  up  to  the  sides  of  the  cone.  Ether  vapor  is  heavy  and 
falls,  hence  the  towel  prevents  waste  and  facilitates  use. 
Do  not  "force  the  ether,"  i.  e.,  let  the  animal  have  plenty  of 
air  to  breathe.  Remember  that  etherization  is  not  asphyxia- 
tion. The  man  giving  the  ether  niiisf  think  of  nothing  else. 
If  the  animal  dies  through  his  fault,  he  must  pay  for  another, 
( 50  cents ) .  Watch  especially  the  respiration,  and  when  in 
floubt,  pinch  foot,  to  see  if  leg  reflex  is  present ;  also  note 
the  corneal  reflex,  which  consists  in  a  closing  of  the  lid 
when  the  cornea  is  lightly  touched.  When  well  under,  the 
animal  should  breathe  regularly  and  quietly.  If  the  respir- 
ation becomes  irregular,  with  pauses,  and  the  reflexes  are 


CIRCULATION   A-\D   RICSriRATlON   OF   MAMMAL. 


139 


present,  the  animal  is  "coming  out"  and  needs  more  ether. 
If  the  respiration  stops,  or  becomes  convulsive,  immediately 
test  the  reflexes,  and  if  the  reflexes  are  absent  and  the  pupil 
is  dilated,  stop  the  ether,  start  artificial  respiration,  and  call 
instructor.  The  amount  of  ether  should  be  lessened  when 
the  third  stage  is  reached,  and  only  a  little  given  at  intervals, 
to  keep  the  animal  asleep.     In  case  coarse  rales  caused  by 

Operation  for  Isolation  of  Carotid  and  Vagus. 


M.  stylohyoideus  major. 
N.  liypoglossal. 

Superior  laryngeal. 

Descendens  noni. 

2  roots  of  depressor  nerve. 

Vagus. 

Depressor. 

Sympathetic. 

Carotid  artery. 

Trachea. 

M.  sterno-mastoid 


Fig.  31.     Dissection  of  nerves  of  left  side  of  neck  of  rabbit.     The  trachea  has 
been  pulled  to  the  right  and  the  nerves  to  the  left. 

collection  of  mucus  are  heard,  swab  out  the  throat  with 
absorbent  cotton  on  large  forceps. 

When  the  animal  is  sufficiently  under  to  have  stopped 
struggling,  fasten  it  on  animal-board,  by  placing  a  noose 
about  each  leg  above  the  hock,  and  tying  the  cords  to  the 
cleats  on  the  sides  of  the  animal-board.  Put  head  in  head- 
holder.    The  instructor  will  show  the  method  of  application. 

As  soon  as  the  animal's  head  has  been  placed  in  the 
head-holder,   remove  the  hair   from   front  of  throat   for  a 


140  EXPERIMENT  XXV. 

space    1.5   in.   wide,   and   from  top   of  thyroid   cartilage   to 
sternum.     Put  the  hair  in  a  battery  jar. 

Sponge  ofif  the  loose  hairs,  and  as  soon  as  the  reflexes 
have  ceased  make  a  median  incision  with  scalpel  through 
skin,  from  top  of  thyroid  cartilage  to  near  top  of  sternum. 
Avoid  veins  at  lower  part  of  incision.  Cut  through  the 
platysma  muscle  in  the  median  line.  Tie  off  any  large 
vessels  that  have  been  cut,  and  have  assistant  sponge  off 
blood  with  warm  salt  solution.  Separate  sterno-mastoid 
from  sterno-hyoid ;  this  brings  the  sheath  of  carotid  artery 
into  view.  Close  to  the  artery  are  the  veins  and  nerves. 
From  this  time  on  it  will  probably  be  bettei  to  tear  away  the 
fascia  longitudinally  with  the  blunt  end  of  an  aneurism  nee- 
dle or  similar  instrument,  rather  than  to  use  a  knife.  The 
descendens  noni  lies  superficially ;  the  vagus  lies  behind  the 
carotid ;  to  the  inside  of  the  vagus  are  the  sympathetic  and 
depressor  nerves.  Isolate  the  vagus,  the  largest  of  these, 
for  a  distance  of  an  inch  or  more  and  pass  a  thread  under 
it,  tying  the  ends  together  so  that  the  nerve  can  be  lifted 
by  the  loop.  Avoid  pinching,  stretching,  or  otherwise 
injuring  the  nerve. 

Prepare  the  dipper  part  of  carotid  for  insertion  of  can- 
nula, by  carefully  separating  it  from  its  sheath  for  a  dis- 
tance of  at  least  an  inch.  Pass 
two  ligatures  under  it,  and  tie 
one  of  them  tightly  at  the 
upper  end  of  the  exposed  part 
of  the  artery ;  place  the  other 
so  that  it  can  be  used  at  short 
Fig.  32.   MeUnod  of  inserting  cann-  noticc    to    tie     the    Cannula    in 

ula  into  carotid  artery.     A,  ligatnre  .-.Ippp  A  nnh^     a     nair  nf     hull 

tied  to  the  distal   side  of  the  place  Pi'iCe.        ^ppi}      a     pair  OI     DUU- 

where  the  cannula  is  to  be  inserted;  rlno-     frirrpnc     'tn,     In-nrAr  i-.at-f     r\i 

B.   cannula;    C,  forceps;   D,   loop  of  ^^^^     lOrCCps     tO     lOWCr  part     Ot 

ligature  placed  around  artery,  to  the    artcrv   tO   shut   off  blood.     There 
proximal   side  of  point  where  can-  - 

nuia  is  to  be  inserted;  E,  bull-dog   are   two   mcthods   of   inserting 

forceps.  .  _  ^ 

a  cannula,  viz:  t.  Grasp  with 
fine  pointed  forceps  as  small  a  part  of  the  arterial  wall  as 
you  can  hold  securely,  and  with  fine  pointed  scissors  make 
a  diagonal  slit  in  the  direction  of  the  heart  and  through 
about  half  the  width  of  the  artery.     Still  holding  the  flap. 


CIRCULATION   AND  RESPIRATION   OF   MAMMAL.  ,141 

insert  the  cannula  which  the  assistant  has  just  taken  from 
the  dish  of  Na^SO^,  and  let  him  tie  it  firmly  with  the  liga- 
ture which  has  been  placed  there  for  the  purpose.  2.  Place 
the  index  finger  of  the  left  hand  beneath  the  artery ;  with 
sharp,  fine  pointed  scissors  make  a  cut  in  the  wall  of  the  ar- 
tery ;  and  without  withdrawing  the  finger  insert  the  cannula. 
It  is  of  advantage  to  put  the  cannula  into  the  upper  part  of 
the  artery,  so  that  the  lower  part  can  be  used  in  case  the 
cannula  has  to  be  put  in  a  second  time.  Fill  cannula  with 
anticoagulation  fluid,  by  means  of  a  fine  pipette,  the  instant 
the  cannula  is  tied  in.  Now  without  losing  time,  place  the 
animal-board  so  that  the  cannula  can  be  readily  connected 
with  the  bulb  on  the  manometer  outfit.  Make  sure  that 
the  cannula,  bulb  and  connecting  tube,  are  full  of  anti- 
coagulation fluid,  and  then  connect  them.  Fasten  the  tube 
of  the  bulb  in  a  burette  clamp,  in  the  position  which  will 
bring  the  least  possible  strain  on  the  artery. 

a.  Measure  of  the  Blood  Pressure  in  the  Carotid. 

As  soon  as  the  cannula  has  been  fastened  to  bulb,  remove 
bull-dog  forceps,  and  make  sure  that  there  is  no  leak  be- 
tween the  cannula  and  the  artery.  The  blood  should  be 
seen  to  enter  the  cannula  and  dififuse  into  the  fluid  in  the 
bulb.  If  all  is  right,  gradually  open  stop-cock  i.  Then 
start  drum  at  rate  of  5  mm.  per  second.  The  manometer 
float  should  rise,  and  the  height  of  arterial  pressure  be 
recorded.  Let  the  drum  run  until  25-30  cm.  have  been 
recorded.  This  record  is  to  be  divided  later  among  the 
students,  the  operator  taking  the  first  part  of  the  curve. 
Notice  that  curve  shows  larger  waves  of  pressure  due  to 
respiration,  and  upon  these,  smaller  waves  caused  by  heart 
beats.  The  small  waves  do  not  show  the  amount  of  blood 
expelled  by  heart,  but  the  efl^ect  of  corresponding  pressure 
changes  in  the  artery,  on  the  mercury  in  the  manometer. 

b.  Maximal  and  Minima!  Blood  Pressures. 

Observe  that  the  valve  L.  controlled  by  cock  2.  per- 
mits fluid  to  pass  only  from  the  manometer,  and  that  the 
valve    M,    controlled    by    cock    3,    permits    it    to    pass    only 


142  EXPERIMENT  XXV. 

toward  the  manometer.  These  valves  permit  us  to  measure 
the  minimal  and  maximal  pressures.  Tlic  mercury  man- 
ometer records  only  the  mean  pressure,  for  the  inertia  of 
mercury  is  too  great  to  permit  it  to  follow  accuratelv  the 
changes  in  blood  pressure.  To  find  the  maximal  pressure, 
first  start  the  drum  and  take  a  short  normal  record,  then 
stop  drum  and  close  stop-cock  i  and  open  cock  3.  The 
float  should  rise  and  record  the  maximal  pressure.  Let 
drum  turn  a  short  distance,  then  stop  drum,  close  cock  3 
and  open  cock  i.  To  Hud  the  minimal  pressure  repeat  the 
procedure,  this  time  opening  cock  2.  The  float  should  fall 
until  it  indicates  the  minimal  pressure. 

c.  Escitation  of  the  Peripheral  Bud  of  the  Right  l^igus. 

The  operator  now  ties  two  ligatures  around  the  vagus 
near  each  other  and  close  to  the  center  of  the  isolated  por- 
tion of  the  nerve,  and  then  cuts  the  nerve  between  them. 
Place  peripheral  end  of  vagus  on  the  electrodes,  taking  care 
that  they  touch  nothing  else.  Close  key  of  primary  circuit ; 
see  that  vibrator  works  well.  Record  a  curve  of  normal 
pressure  for  about  10  seconds  and  then  let  the  apparatus 
man  open  short-circuit  key.  If  weak,  the  current  should 
slow  the  heart,  and  if  strong,  should  stop  it.  Strengthen 
current  if  necessary.  Excite  for  only  about  10  seconds, 
then  close  short  circuit  and  watch  recovery  about  15  sec- 
onds. Repeat  the  experiment  4  times,  to  provide  a  record 
for  each  student,  and  give  an  interval  of  half  a  minute  be- 
tween the  succeeding  tests. 

d.  Record  of  Respiration  ivitJi  Pneumograph. 

Place  a  receiving  tambour  on  a  stand,  so  that  cork  at- 
tached to  the  membrane  rests  against  the  base  of  the  thorax 
of  the  animal  in  the  position  to  give  the  greatest  movement. 
Connect  with  recording  tambour,  shown  at  A  in  Fig.  30. 
Take  record  of  respiration  with  each  of  the  experiments 
of  part  d. 

c.     Excitation  of  Central  End  of  the  J'agus. 

Now  while  taking  record  of  blood  pressure  and  respira- 


CIRCULATION   AXD  RESPIRATION   OF   MAMMAL.  I43 

tion,  excite  central  end  of  vagus  with  weak  current.  Affer- 
ent (sensory)  fibers  are  excited,  resulting  in  the  following: 

I. — Excitation  of  respiratory  center,  causing  change  in 
amount  and  frequency  of  respiration. 

2. — Excitation  of  vaso-motor  center,  causing  usually  a 
rise,  but  occasionally  a  fall  of  blood  pressure. 

3.— Excitation  of  vagus  center,  causing  slowing  of  heart 
and  usually  a  fall  of  pressure,  in  spite  of  vaso-constriction 
which  may  occur. 

4. — If  current  is  too  strong,  and  the  anaesthesia  incom- 
plete, there  may  be  reflex  excitation  of  motor  centers,  caus- 
ing convulsive  movements  which  may  mask  the  other  effects 
and  cause  a  rise  of  blood  pressure. 

Now  let  the  student  tie  off  the  right  carotid  below  can- 
nula ;  remove  cannula  from  artery ;  hold  a  dish  under  the 
cannula  and  then  disconnect  bulb  from  manometer  tube ; 
wash  bulb  and  cannula  out  thoroughly ;  connect  bulb  again 
with  manometer ;  put  cannula  in  dish  of  Na^So^.  Handle 
bulb  and  cannula  with  care,  as  they  are  fragilt  and  hard 
to  replace.  Sponge  up  all  fluid  spilled  and  put  apparatus  in 
order  for  next  experiment.  Disconnect  and  remove  pneu- 
mograph. 

/.     Excitation  of  Peripheral  End  of  Left  Vagus. 

The  student  who  is  to  operate,  takes  the  animal-board 
to  the  operating  table  and  proceeds  to  prepare  the  artery 
and  nerve  of  the  left  side,  the  other  students  doing  the  work 
assigned  in  the  schedule.  When  the  operation  is  finished, 
test  and  record  normal  blood  pressure  as  before.  Any  ex- 
]:)eriments  not  successful  on  right  side  may  be  repeated.  In 
any  case  the  operation  is  to  be  done  and  a  normal  record 
taken. 

g.     Excitation  of  Sciatic  Nerve. 

The  sciatic  nerve  lies  beneath  the  vastus  externus  on  the 
middle  of  the  external  surface  of  the  thigh.  Remove  hair 
over  region :  cut  skin  longitudinally  for  2  inches ;  cut 
through  vastus  externus  and  expose  the  nerve.  Animal 
must  he  well  under  the  ether  before  nerve  is  handled,  and 
II 


144  EXPERIMENT  XXV. 

especially  on  stimulating.  Pass  a  ligature  under  nerve  and 
tie  ends  together.  When  ready  to  excite,  ligate  peripheral 
end  of  part  exposed  and  cut  peripherally  to  ligature ;  place 
nerve  across  electrodes,  which  must  not  touch  anything  else, 
then  apply  current.  See  rise  of  blood  pressure  due  to  re- 
flex vaso-constriction,  or,  as  not  infrequently  occurs  a  fall 
due  to  reflex  vaso-dilation  (see  Howell,  p.  541).  If  cur- 
rent is  too  strong  or  animal  not  well  under,  convulsive  move- 
ments will  be  produced  which  will  mask  the  effect  desired. 

/;.     Blood  Pressure  during  Asphyxia. 

Expose  the  trachea  and  place  lozv  dozmi  upon  it  a  clamp 
used  for  rubber  tubing,  so  that  the  trachea  can  be  closed 
off  quickly.  Start  drum  at  rate  of  one  or  two  mm.  per 
second,  then  clamp  off  trachea,  marking  the  instant  this  is 
done  by  means  of  short  circuit  key.  Observe  the  following 
stages : 

I. — Dyspnoea.  Blood  pressure  rises  gradually.  Deep 
and  prolonged  respirations,  with  short  expirations,  soon 
affect  the  blood  pressure  in  a  marked  manner. 

2. — Convulsions.  Each  convulsion  is  accompanied  by 
a  rise  of  blood  pressure. 

3. — Weakening  and  slowing  of  heart  beats ;  respirations 
feebler  and  fewer ;  finally  both  heart  beats  and  respirations 
stop. 

/.     Elasticity  of  Lniig  Tissue. 

Make  incision  in  trachea ;  insert  cannula ;  and  connect 
with  a  water  manometer,  noting  the  level  of  the  fluid.  Open 
the  chest  and  observe  the  rise  of  water  in  tube  when  air 
enters  chest  and  lungs  collapse.  To  open  chest,  first  make 
an  incision  with  knife  over  the  entire  length  of  the  sternum ; 
grasp  ensiform  cartilage  with  strong  forceps ;  push  point 
of  shears  or  bone  forceps  through  chest  wall  at  end  of 
ensiform  cartilage  and  cut  sternum  lengthwise,  in  the 
median  line,  to  within  an  inch  of  its  upper  end.  Keep  point 
of  shears  close  to  sternum,  to  avoid  cutting  lungs  or  other 
organs.  Pull  the  cut  edges  of  the  sternum  apart  and  see 
the  collapsed  lungs.     Note  the  amount  of  elastic  contraction 


CIRCULATION   AND  RESPIRATION   OF   MAMMAL.  1 45 

of  the  lungs,  as  measured  by  height  of  rise  of  water  in  man- 
ometer. 

NOTES. 

In  mounting  the  curves,  be  careful  to  preserve  the  part 
of  each  record  which  shows  the  relation  of  writing  points, 
and  the  portion  showing  lo  seconds  before,  and  15  seconds 
after  the  period  of  stimulation.  Draw  long  vertical  lines 
across  the  curve,  to  the  top  of  the  paper,  at  points  4  seconds 
before  stimulation,  at  the  end  of  stimulation,  and  10  seconds 
after  stimulation ;  also  draw  shorter  verticals  at  a  distance 
of  3  seconds  on  each  side  of  the  long  verticals  and  cutting 
the  respiration  and  blood  pressure  curves. 

To  find  the  blood  pressure,  measure  from  the  base  line 
given  by  the  time  signal  to  the  middle  of  the  highest  pulse 
beat  near  a  long  vertical,  and  multiply  by  two.  For  heart 
rate,  count  the  pulse  beats  in  the  6  seconds  between  the  short 
verticals  and  multiply  by  10.  In  a  similar  manner  determine 
the  number  of  respirations  per  minute.  Write  the  figures 
obtained,  on  the  cardboard  above  the  mounted  curve,  at 
points  corresponding  to  the  observations. 

In  the  notes  accompanying  the  curves,  state  the  cause 
of  the  changes  in  arterial  pressure,  pulse,  and  respiration 
caused  by  the  excitations.  Give  brief  statements  of  the 
results  obtained  under  each  of  the  subheadings  of  the 
experiment. 


146 


F,Xr'KK IMF/NT   XXV. 


CIRCULATION   AND  RESPIRATION   OF    MAMAIAL. 


147 


148 


KXPERIMENT  XXV. 


CIRCULATION   AND   RESP1RATI(3N   OF   MAMMAL.  I49 

EXPERIMENT  XX\  I. 

Circulation  and  Respiration  of  the  Mammal,  Continued. 

a.  Exciiatioii  of  Rii:;lit  Depressor  Xerze. 

Tlie  depressor  is  an  afferent  nerve  from  the  root  of  the 
aorta,  and  hence  excitation  of  the  peripheral  end  has  no 
cft'ec  .  Excitation  of  central  end  has  little  effect  on  the 
cardiac   centers,   but   causes   dilation   of   peripheral   vessels. 

Expose  the  carotid  as  in  Experiment  XXV.  To  find 
the  depressor,  remember  that  vagus  lies  behind  artery  and 
the  depressor  and  the  sympathetic  to  the  inner  side.  High 
up  tlie  vagus  gives  off  a  transverse  branch,  the  superior 
laryngeal,  (see  diagram,  Experiment  XX\")  to  the  larynx. 
The  depressor  arises  as  a  very  slender  nerve  by  two  branches 
from  this,  or  one  from  this  and  one  from  the  vagus.  Find 
the  place  of  division,  then  trace  the  nerve  down  for  an  inch 
or  more,  tie  a  thread  about  it  and  cut  peripherally  to  thread. 
Handle  nerve  with  utmost  care  and  see  that  it  does  not  dry. 

Now  isolate  carotid  and  insert  cannula,  connect  with 
manometer ;  apply  pneumograph  ;  record  normal  curves  of 
blood  pressure  and  respiration.  Excite  central  end  of  de- 
pressor while  drum  is  running.  The  latent  period  is  long. 
Excite  only  long  enough  to  produce  an  evident  effect,  and 
let  drum  run  till  recovery  is  well  under  way.  Take  four 
records,  waiting  in  each  case  until  recovery  is  complete. 
Notice  that  rate  of  heart  is  practically  unchanged. 

b.  Bxcitation  of  Left  Depressor  Xerve. 

Prepare  depressor  and  carotid  of  other  side  and  repeat 
above  experiment. 

c.  Tracheotomy  and  Artificial  Respiration. 

Remove  cork  of  bottle  in  outfit  for  artificial  respiration, 
put  about  an  inch  of  ether  in  the  bottom,  replace  the  cork. 
Make  an  incision  in  the  trachea,  insert  the  cannula,  and  tie 
it  firmly   in   place  with   a   strong  ligature.      Now   give  the 


150  EXPERIMENT  XXVI. 

ether  by  holding  the  cone  above  the  tracheal  cannula.  To 
open  the  chest,  first  make  an  incision  with  knife  over  entire 
length  of  sternum,  grasp  ensiform  cartilage  with  strong  for- 
ceps ;  push  point  of  shears  or  bone  forceps  through  chest 
wall  at  end  of  cartilage  and  cut  sternum  lengthwise,  in  the 
median  line  to  within  one  inch  of  its  upper  end.  Keep  point 
of  shears  close  to  sternum  to  avoid  cutting  lungs  or  other 
organs.  Special  care  is  necessary  at  the  upper  part,  or  blood 
vessels  will  be  cut.  While  this  is  being  done,  the  apparatus 
man  should  prepare  artificial  respiration  apparatus  and  test 
the  amount  of  ether  it  gives.  Regulate  supply  of  ether  by 
means  of  clamps  on  tubes  connecting  with  ether  bottle. 

As  soon  as  the  chest  is  opened,  with  clamp  on  side  tube 
open,  connect  tracheal  cannula  with  ether  bottle,  and  start 
bellows,  pumping  at  rate  of  once  a  second.  Screw  up 
clamp  on  side  tube  until  the  lungs  are  seen  to  expand  and 
relax  well. 

Observe  the  effect  of  artificial  respiration  on  the  curve 
of  blood  pressure.  The  respiratory  waves  of  the  curve  are 
now  reversed,  the  curve  falling  soon  after  the  air  begins  to 
enter  the  lungs,  and  rising  soon  after  beginning  of  expir- 
ation, due  to  elastic  recoil  of  lung. 

d.     The  Current  of  Action  of  the  Heart. 

Draw  chest  walls  apart  with  the  hooks  provided.  Open 
the  pericardium  widely,  taking  care  not  to  cut  the  heart  in 
doing  so.  Now  hold  the  bone  of  a  nerve-leg  preparation  in 
forceps,  with  nerve  hanging  down  ;  let  the  nerve  lie  upon  the 
beating  ventricle  lengthwise ;  the  muscle  should  contract 
with  each  beat.  If  it  does  not,  lift  it  and  try  again.  The 
warm  blood  quickly  injures  the  nerve,  and  hence  the  latter 
should  not  be  left  long  in  contact,  until  the  desired  effect 
is  seen. 

c.     Ohservation  of  Exposed  Heart  during  Vagus  Excita- 
tion. 

Observe  the  effect  of  excitation  of  the  peripheral  end  of 
a  vagus  nerve  on  the  rate  and  strength  of  beat  of  the  ex- 
posed heart.     Test  with  weak,  medium,  and  strong  currents 


CIRCULATION   AND  RESPIRATION  OF  MAMMAL.  151 

/.     Tension  of  Ventricle  during  Systole  and  Diastole. 

Take  the  ventricle  gently  between  the  thumb  and  fingers, 
and  feel  it  harden  with  each  systole. 

g.     Observation  of  the  Changes    in    Heart  during  Death 
from  Asphyxia. 

Open  chest  wadely  so  as  to  obtain  a  good  view.  Stop 
artificial  respiration  and  observe  the  effects  of  asphyxia  on 
the  rhythm  of  auricles  and  ventricles  as  the  heart  dies.  Make 
notes  of  the  order  in  which  the  strength  of  beat  of  auricles 
and  ventricles  changes.  Notice  any  irregularities,  and 
which  auricle  or  ventricle  gives  out  first.  What  part  of 
heart  is  most  distended  at  death? 

h.     Innervation  of  Diaphragm  by  the  Phrenic  Nerves. 

These  nerves  are  easily  found,  running  down  lateral 
and  posterior  sides  of  pericardium.  Excite  one,  then  the 
other,  observing  contraction  of  diaphragm  from  upper  side. 
Open  the  abdominal  cavity  by  one  incision  in  median  line ; 
observe  relations  of  organs ;  push  viscera  down  and  excite 
phrenic  while  looking  at  under  side  of  diaphragm.  Notice 
that  contraction  of  diaphragm  depresses  the  floor  of  the 
chest ;  thus  increasing  chest  cavity  and  lessening  abdominal 
cavity. 

/.     Peristalsis  of  Intestines. 

Observe  any  peristaltic  movements  that  may  occur  be- 
cause of  exposure  to  air  and  loss  of  blood.  See  direction 
of  waves.  Watch  for  anti-peristalsis.  Try  effect  of  mechan- 
ical and  electrical  stimulation  of  stomach  and  intestines. 
Excite  bladder  electrically. 

NOTES. 

Write  up  the  notes  as  directed  in  the  preceding  experi- 
ment. 


152  EXPERIMIvNT  XXVI. 


CIKCUI.ATION    AND  RESPIRATION   Of   MAMMAL.  1 53 


154  EXPERIMENT  XXVI. 


CAROTID  PULSE  OF  MAN.  155 

EXPERIMENT  XXVIL 

The  Carotid  Pulse  in  Man. 

a.     The  Ponii  of  the  Pulse. 

Mount  a  recording  tambour  on  a  stand  and  connect  it 
with  an  open  tambour  designed  for  carotid  artery,  leaving 
side  tube  open.  See  that  the  lezxr  of  the  tambour  is  hor- 
kontal.  Apply  the  open  tambour  to  the  skin  of  the  neck 
over  the  artery,  and  fasten  it  in  place  with  the  U-shaped 
spring,  placing  the  ball  of  the  spring  in  the  socket  on  the 
back  of  the  tambour  and  placing  the  block  against  the 
opposite  side  of  the  neck.  Then  test 
the  working  of  the  outfit  by  pinching 
the  side  tube.  With  each  heart  beat 
there  should  be  an  excursion  of  the 
lever  of  at  least  5  mm.  Adjust  posi- 
tion of  tambour  on  neck,  and  pressure 
of  spring  to  give  the  largest  pulsation, 
then  bring  writing  point  very  lightly 

I^'ig- 33-      Tambour  and  .  /-  <->,       ,      i 

neck  spring  used  to  study  agauist  drum.  btart  drum  at  5  mm. 
A ^ sprhig*^  '^B'°ban-and-  per  secoud,  closc  side  branch  with 
open'ti±ur?c!'l'iock'  Spring  dip  and  record  the  curve  of  the 
pulse. 
Unless  the  friction  of  writing  point  upon  drum  is  made 
as  slight  as  possible,  small  waves  of  the  pulse  curve  will  be 
obscured.  Mark  on  the  curves  to  indicate  the  primary 
wave  and  the  dicrotic  notch.  The  former  results  from  the 
systole  of  the  ventricle,  and  the  latter  from  relaxation  of 
the  ventricle  and  closure  of  the  semilunar  valve.  The 
dicrotic  notch  therefore  divides  the  pulse  into  its  systoHc 
and  diastolic  portions,  and  is  to  be  looked  for  at  about  the 
end  of  the  first  third  of  the  curve.  Do  pre-dicrotic  or  post- 
dicrotic  waves  occur  in  the  record?  Take  records  with  four 
widely  different  speeds  of  drum,  and  observe  the  effect  on 
the  form  of  the  curve. 

h.     The  Pulse  Rate. 

Mount  a  time  signal  to  write  below  the  pulse  curve,  con- 
nect it  with  the  clock  circuit,  start  drum  at  5  mm.  per  sec- 


156  EXPERIMENT  XXVII. 

ond,  and  record  the  curves  of  time  and  pulse.  Draw  per- 
pendiculars at  intervals  of  ten  seconds  cutting  the  pulse 
curve,  and  determine  the  rate  of  the  pulse  for  three  cc«i- 
secutive  periods  of  ten  seconds. 

c.  Dnrafioji  of  Systole  and  Diastole. 

Mount  a  fork  in  place  of  the  time  signal  and  record 
curves  .of  pulse  and  fork  with  the  fastest  speed  of  drum 
given  by  clockwork.  Then,  without  moving  drum,  remove 
clip  from  side  tube,  and  record  a  base  line  for  the  pulse 
curve.  When  the  curves  have  been  fixed,  draw  arcs  with 
dividers  from  beginning  of  primary  wave  and  from  bottom 
of  dicrotic  notch  to  the  base  line,  using  a  radius  equal  to 
the  length  of  the  writing  lever  and  centers  on  the  base  line. 
Draw  perpendiculars  from  the  points  where  the  arcs  cut 
the  base  line,  through  the  fork  curve.  Count  up  the  fork 
waves  between  the  perpendiculars,  and  thus  determine  the 
duration  of  systole  and  diastole.  Make  this  determination 
for  five  consecutive  pulse  beats  and  state  the  average  in 
your  notes.  Results  should  be  changed  to  looths  of  a 
second  by  using  number  found  in  calibrating  fork. 

d.  Effect  of  Exercise.     ' 

Go  through  the  form  of  taking  a  normal  record,  as  in  c, 
to  make  sure  that  the  neck  tambour  is  properly  adjusted, 
and  that  the  recording  tambour  is  writing  well.  Then, 
without  moving  the  drum  or  either  tambour,  detach  the 
rubber  tube  where  it  joins  the  glass  T.  Take  a  quick  rim 
down  stairs  and  back,  connect  up  the  tambour  as  soon  as 
possible,  and  record  the  accelerated  pulse.  Determine  dur- 
ation of  systole  and  diastole  as  before. 

Which  changes  most  in  the  quickening  of  the  pulse  due 
to  work,  the  systolic  or  the  diastolic  portion?  Are  any  other 
changes  in  the  pulse  curve  to  be  observed?  If  so,  describe 
them. 


CAROTID  PULSE  OF  MAN.  1 57 


158 


F.XrF.RlMICNT  XXVII. 


I^ORM  AND  POSTPONEMENT  OE  RADIAL  PULSE. 


^59 


EXPERIMENT  XXVIII. 
The  Radial  Pulse   Studied    by    the    Tambour  Method. 


a.     Form  of  Radial  Pulse. 

Connect  a  recording  tambour  with  a  tambour  designed 

for  radial  artery,  leaving  side  branch  of  tube  open.    Arrange 

arm  rest  and  tambour  as 
shown  in  the  diagram.  Mark 
the  point  on  left  wrist  where 
strongest  pulse  is  felt.     Sub- 


Fig.  34.  Method  of  applying  tani" 
bour  to  wrist,  to  obtain  sphygmo- 
gram  from  the  radial  artery.  A, 
cross  section  of  wrist;  B,  back  board 
of  arm  support;  C,  cabinet  maker's 
clamp;  D,  clamp  fastening  L  rod  to 
the  horizontal  rod  of  arm  rest;  E, 
clamp  fastening  tube  of  tambour  to 
short  arm  of  L  rod;  F,  tambour  with 
disk,  and  prop  to  rest  on  artery. 


ject  seats  himself  comfortably 
in  chair,  holding  one  end  of 
arm  rest  in  lap,  while  other 
end  is  placed  on  table  or  stool 
so  as  to  tilt  it  at  a  suitable 
angle  for  the  arm  to  rest  eas- 
ily. Place  arm  on  rest  with 
marked  point  toward  tam- 
bour ;  fasten  thumb  with  loop 
of  cloth,  using  holes  in  back 
board  :  apply  button  of  tambour  to  marked  spot,  and  adjust 
tambour  so  that  rod  bearing  button  is  in  line  with  tube  of 
tambour  and  perpendicular  to  surface  of  wrist.  Vary  the 
])ressure  on  artery  by  sliding  tube  of  tambour  in  clamp 
until  largest  pulsation  is  given.  An  excursion  of  3-5  mm. 
with  each  heart  beat  should  be  secured,  but  a  smaller  move- 
ment will  suffice  where  this  cannot  be  obtained.  The  arm 
must  be  relaxed  and  perfectly  quiet.  Record  the  radial 
pulse  on  a  drum  and  observe  whether  the  same  waves 
appear  as  in  the  carotid  pulse. 

b.     Postponement  of  the  Radial  Pulse. 

Arrange  to  write  carotid  and  radial  pulse  and  fork 
curve  in  same  vertical  line.  Make  sure  that  the  levers  of 
the  tambours  are  horizontal.  Mark  relative  position  of 
points,  then  record  the  three  curves  with  fastest  speed  given 


l6o  EXPERIMENT  XXVIII. 

by  kymograph.  Without  disturbing  apparatus,  remove 
cHps  from  side  tubes  and,  with  the  levers  horizontal,  record 
base  lines  for  the  two  pulse  curves. 

Fix  the  tracing,  and  then,  with  centers  on  the  base 
lines  and  the  lengths  of  the  levers  as  radii,  draw  arcs  from 
beginnings  of  corresponding  primary  waves  to  their  respec- 
tive base  lines ;  then  correcting  for  positions  of  points,  draw 
perpendiculars  through  fork  curve  and  find  duration  of 
postponement  of  radial  pulse  as  compared  with  carotid 
pulse.     Take  average  for  three  consecutive  beats. 


FORM  AND  POSTPONEMKNT  OF  KADIAL  PULSE.  l6l 


l62 


kxi'f,r]mp:nt  xxviii. 


INFLUENCES  AFFECTING  RADIAL  PULSE. 


163 


EXPERIMENT  XXIX. 

The  Radial  Pulse  as  Recorded  by  the  Jacquet  Sphygmo- 

graph. 

This  is  probably  the  most  useful  instrument  for  exam- 
ination of  the  pulse  that  we  have.  It  is  fragile,  and  must  be 
handled  with  care  and  returned  in  good  condition.  The 
strap  A   is  buckled  about  the  left   wrist,   with  the  end  B 


Fig-.  35.     Scheme  of  Jacquet's  sphygniog^raph. 

toward  the  hand.  The  instrument  slips  into  groove  C  of 
base,  and  thumb-screw  D  is  turned  into  socket  E.  The 
paper,  shown  in  cross  section  at  F,  runs  between  the  roller 
G  and  two  small  wheels  above  it.  Clock  for  moving  paper 
is  wound  by  means  of  large  thumb-nut  H,  started  and 
stopped  by  lever  at  /,  and  lever  /  gives  a  change  of  speed. 
Clockwork  for  time  marker  L,  is  wound  by  means  of  thumb- 
nut  K,  and  gives  fifths  of  a  second.  M  is  a  clasp  for  hold- 
ing L  up  out  of  harm  when  not  in  use.  Button  iV  is  pressed 
on  artery  by  cam  wheel  P,  turned  by  thumb-nut  Q,  to  vary 
the  pressure.  Movements  of  iV,  are  transmitted  through 
rod  R,  to  lever  S,  turning  on  axis  T,  thence  to  lever   U. 


164  EXPERIMENT  XXIX. 

turning  on  axis  V,  and  finally  to  marker  W.     Position  of 
writing  point   on   paper   is   regulated   by   thumb-screw   D. 

CAUTIONS. 

(i)  Be  careful  not  to  injure  the  time  marker.  Raise 
and  lower  it  with  the  fine  point  of  a  knife  or  pencil.  It 
must  ahcvays  be  lifted  into  clasp  before  reiroving  the  paper. 

(2)  Avoid  bending  the  writing  pointer  when  inserting 
the  paper. 

(3)  Do  not  wind  the  clockwork  too  tight. 

(4)  Instrument  must  be  held  level  to  record  time  accu- 
rately. 

( 5 )  Pressure  on  artery  is  regulated  by  sinall  move- 
ment of  cam. 

a.  Normal  Curies  and  Effect  of  Position  of  Body. 

Place  several  strips  of  paper  around  a  large  drum,  and 
blacken  as  usual,  cutting  the  strips  loose  as  needed.  Place 
end  of  a  strip  between  roller  and  wheels,  start  clockwork, 
and  run  the  paper  in,  to  the  extent  of  one  inch. 

Having  adjusted  instrument  so  as  to  give  the  largest 
pulsation,  proceed  to  make  records  while  sitting  and  stand- 
ing quietly,  using  slow  speed  of  paper.  In  this  and  all  sub- 
sequent tests,  take  care  not  to  move  arm  or  hand  when  the 
record  is  being  written.  Report  the  rate  as  recorded  for 
six  seconds. 

b.  Effect  of  Compressing  Brachial  Artery. 

While  the  tracing  is  being  taken,  compress  the  brachial 
artery  with  hand  or  a  tourniquet. 

c.  Effect  of  Deglutition. 

Start  the  paper  at  the  fast  rate,  record  a  few  beats,  then, 
while  record  continues,  take  several  swallows  of  water  in 
quick  succession,  marking  on  the  record  the  e.vact  time 
when  the  swallowing  begins  and  ends.  Determine  the  rate 
before,  during,  and  after  swallowing.  The  increase  in  rate 
is  explained  as  a  lessening  of  vagus  influence.  The  swal- 
lowing center  is  in  the  medulla  oblongata  not  far  from  the 


INFLUENCES  AFFECTING  RADIAI.  PUESE.  165 

vagus  inhibitory  center,  and  nervous  impulses  overflowing 
from  the  former  inhibit  the  latter. 

d.  Effect  of  Inhalation  of  Aniyl  Nitrite. 

Slow  speed  of  paper.  Record  normal  pulse  for  10  beats, 
then  begin  to  inhale  a  drop  of  amA-l  nitrite  that  will  be 
placed  upon  a  handkerchief  by  the  instructor.  Associate 
should  mark  on  record  the  exact  time  of  inhalation.  Con- 
tinue record  to  end  of  paper.  This  drug  acts  chiefly,  when 
taken  in  sm.all  amounts,  on  the  muscles  in  the  walls  of  the 
small  vessels,  causing  a  dilation.  Fall  of  blood  pressure 
and  increased  dicrotism  of  the  pulse  results.  The  change 
in  the  level  of  the  writing,  frequently  seen,  cannot  be  taken 
as  evidence  of  the  diminished  arterial  pressure.  The  writ- 
ing point  must  be  placed  high  before  the  inhalation  occurs, 
or  it  will  run  off  the  lower  edge  of  the  paper.  Do  not  re- 
peat. 

e.  l\ilsalz'a's  Experiment. 

This  experiment  and  the  following  one  are  not  without 
danger,  and  should  not  be  practiced  to  excess,  nor  by  any- 
one with  an  abnormal  heart  or  arteries. 

Record  10  normal  beats,  then  take  a  deep  breath,  and, 
with  mouth  and  nostrils  closed,  make  a  strong  expiratory 
effort  for  eight  or  ten  seconds,  then  breathe  freely.  Mark 
time  of  each  stage  on  record.  Report  effect  on  rate  and 
shape  of  pulse  curve.  The  latter  is  especially  interesting. 
The  expiratory  effort  drives  the  blood  out  of  the  chest  into 
the  arteries,  and  prevents  entrance  of  venous  blood  into  the 
chest  by  compressing  veins  and  right  heart. 

/.     Mailer's  Experiment. 

Record  ten  beats,  then  exhale  as  completely  as  possible, 
and  with  mouth  and  nostrils  closed  make  a  strong  inspiratory 
effort  for  ten  seconds,  then  breathe  freely.  Mark  on  record 
and  report  as  before.  The  forced  inspiration  tends  to  keep 
the  heart  and  large  vessels  dilated,  tends  to  prevent  blood 
from  leaving  chest,  and  causes  a  rush  of  blood  into  the  chest 
bv  way  of  the  veins. 


I  66  EXPERIMENT   XXIX. 

The  sphyginograph  cannot  give  a  measure  of  blood 
pressure.  The  changes  to  be  observed  in  the  level  of  the 
curve  are  in  part  due  to  alteration  of  the  amount  of  dis- 
tension of  the  venae  comites  about  the  arterv. 


INFLUENCES  AFFECTING  RADIAL  PULSE.  167 


1 68  EXPERIMENT  XXIX. 


CIRCULATION   IN   FOOT  OF  FROG.    .  169 


EXPERIMENT  XXX. 

Capillary  Circulation  in  the  Web  of  the  Foot  of  a  Frog. 

Destroy  the  brain  of  a  frog  by  a  pithing  needle,  and 
plug  the  skull  cavity  with  a  pointed  match.  Be  sure  to  have 
the  match  ready  to  insert  at  the  instant  the  pithing  needle 
is  withdrawn,  so  that  the  least  possible  blood  shall  be  lost. 
Wrap  frog  in  moist  cloth  and  place  on  special  frog-board, 
face  down,  and  spread  the  web  over  the  opening,  keeping 
in  place  by  pins  through  outer  toes.  Avoid  stretching  web 
too  tightly,  and  keep  it  moist,  not  wet.  Place  board  on 
microscope  stage. 

Examine  first  with  low  power.  If  the  blood  is  not  seen 
to  circulate  through  the  smaller  vessels,  the  web  has  prob- 
ably been  stretched  too  tightly,  or  the  frog  has  not  recovered 
from  the  shock  caused  by  pithing.  Decide  which  of  the  ves- 
sels are  arteries,  capillaries  and  veins,  observing  where  the 
blood  flows  from  large  to  small  and  from  small  to  large  ves- 
sels, where  the  blood  stream  is  most  rapid  and  where  it 
pulsates. 

I.  Now   choosing    a    small   artery,   observe    with    higher 

power  the  following  points : 

a.  Pulsating  stream. 

b.  Rapid  axial   stream ;   lighter,   peripheral   layer, — the 

"inert  layer." 

c.  Eddies  of  the  stream  at  a  bifurcation. 

II.  Examine  a  small  vein  and  observe: 

a.  Constant  stream   (sometimes  pulsating  if  the  shock 

from  the  pithing  has   not  been   recovered   from, 
and  there  is  vaso-dilation). 

b.  Slower  current,  and  less  marked  "inert  layer"  than 

in  artery. 

III.  Examine  capillaries,  and  observe: 

a.  Frequent  anastomoses. 

b.  Condition  and  behavior  of  corpuscles. 
A.     Red  corpuscles  (erythrocytes). 

I.     Shape,  transparency,  color. 


lyo  EXPERIMENT    XXX. 

2.  The  number  that  can  pass  abreast  in  a  cap- 

illary. 

3.  Position   of   long   axis    with   respect   to   cur- 

rent. 

4.  Elasticity,   and  change   in   shape  when  com- 

pressed, or  when  turning  a  corner. 

5.  Passage     through     a     capillary     apparently 

smaller  than  cell. 
B.     White  corpuscles  (leucocytes). 

1.  Shape  and  color. 

2.  Peripheral  arrangement. 

3.  Slow  progression,  and  rolling  motion. 

IV.  Vaso-inotor  Action. 

Expose  sciatic  nerve,  using  the  utmost  care  not  to  injure 
the  blood  vessels.  Cut  high  up,  and  dividing  branches, 
raise  from  wound  and  lay  on  a  piece  of  moist  filter  paper 
placed  over  the  skin.  (There  is  an  acid  secretion  on  the 
skin  which  will  injure  the  nerve.)  Of  course  the  nerve 
must  be  handled  as  little  as  possible  and  never  be  com- 
pressed. Now  excite  nerve  with  induction  current  "at  the 
same  time  that  a  suitable  part  of  the  web  is  being  examined 
with  a  low  power.  The  vessels  should  be  seen  to  grow 
smaller  and  the  circulation  should  be  consequently  slowed, 
or  stopped. 

V.  Diapedesis,  i.  e..  Migration  throngh  Wall  of  Capillary. 
(This   is   optional.)      This   is   not   often   seen   to  occur 

under  normal  conditions,  but  the  phenomenon  is  of  frequent 
occurrence  when  an  irritant  cavises  local  inflamation.  This 
can  be  best  studied  in  the  mesentery,  a  slight  burn  from  a 
hot  glass  rod  being  a  suitable  irritant. 

Examine  with  low  power  the  effect  upon  the  circulation 
of  the  part.  Then  choosing  a  capillary  whose  walls  can  be 
seen  distinctly,  watch  carefully  a  leucocyte  resting  against 
the  wall,  and  observe  its  change  of  shape  as  it  passes 
through  the  wall.  Make  drawing  illustrating  the  method 
of  progression.  Red  corpuscles  do  not  pass  through,  unless 
the  walls  have  been  greatly  injured,  since  they  do  not 
possess  amoeboid  power. 


CIRCULATION    IN   FOOT  OF   FROG.  171 


172  EXPERIMENT    XXX. 


HUMAN  BLOOD  PRESSURE.  1 73 


EXPERIMENT  XXXI. 

Measurement    of    Human    Blood    Pressure    in    Different 
Positions. 

The  blood  pressure  is  a  measure  of  the  potential  energy 
available  for  overcoming  the  resistance  offered  by  the  walls 
of  the  vessels  to  the  flow  of  the  blood.  Arterial  blood 
pressure  is  a  measure  of  the  status  of  the  following  factors 
upon  which  it  is  dependent,  viz :  the  amount  of  energy 
imparted  by  the  heart  to  the  blood,  (varying  with  rate  and 
strength  of  beat,  and  volume  of  output),  and  the  amount 
of  resistance  encountered  by  the  blood,  (varying  with  the 
friction  in  the  large  vessels,  determined  largely  by  the 
elasticity  of  the  walls,  and  with  the  friction  in  the  small 
vessels,  determined  chiefly  by  the  action  of  the  vaso-motor 
nerves).  Since  a  high  blood  pressure  means  excessive 
work  for  the  heart,  and  since  a  very  low  blood  pressure 
means  that  too  little  blood  is  being  pumped,  (because  of  lack 
of  blood,  imperfect  heart  action,  or  valvvilar  lesions),  or  that 
the  vessels  are  abnormally  dilated,  it  is  evident  that  a  meas- 
ure of  the  arterial  pressure  is  of  diagnostic  importance. 

If  one  presses  with  the  tip  of  a  finger  upon  the  skin 
over  an  artery,  at  first  very  lightly,  and  then  with  more  and 
more  strength,  he  feels  first  a  slight  thrill,  then  a  stronger 
pulse,  and  finally  a  lessening  of  the  pulse,  until  it  is  alto- 
gether lost,  except  at  the  side  of  the  finger  nearer  the  heart. 
If  the  finger  is  gradually  removed,  these  sensations  are  felt 
in  the  reverse  order.  With  practise  a  fairly  accurate  esti- 
mate of  the  arterial  pressure  can  be  obtained  in  this  way. 

Apparatus. — A  sphygmomanometer  is  an  instrument 
devised  to  measure  more  accurately  than  the  finger,  the 
systolic,  i.  e.  maximal  arterial  pressure,  and  in  the  case 
of  the  Erlanger  instrument,  to  also  record  the  pulsations 
as  a  means  of  estimating  the  diastolic  pressure. 

The  Riva-Rocct  Sphygmomanometer. — The  instru- 
ment (see  Fig.  ;^6)   consists  of  a  reservoir  of  mercury,  to 


174 


EXPERIMENT   XXXI. 


the  bottom  of  which  a  capillary  manometer  tube  passes, 
and  which  connects  with  a  rubber  cuff,  which  is  strapped 
over  the  internal  surface  of  the  upper  arm  at  the  seat  of 
the  brachial  artery,  by  a  broad  unyielding  band  of  leather. 
Air  is  pumped  into  this  system  by  a  bulb,  and  is  let  out 
again,  either  rapidly  through  an  outlet  tube,  or  slowly 
through  a  fine  pin  hole  in  the  cap  of  a  vertical  tube,  con- 
trolled by  the  finger.  A  three-way  cock  permits  communi- 
cation to  be  made  between  the  inflating  bulb  and  the  cuff, 
and  between  latter  and  the  outlet  tube. 

Gaertner's  Tonometer. — This  instrument  permits  one 
to  know  what  pressure  applied  to  the  second  joint  of  the 
finger,  will  prevent  the  blood  from 
entering  the  finger,  as  shown  by  the 
sensation  and  change  of  color  which 
follow  the  return  of  the  blood.  Gaert- 
ner  considers  this  to  be  the  mean 
arterial  pressure.  The  instrument 
consists  of  a  mercury  manometer,  con- 
nected with  a  pneumatic  ring,  to  be 
placed  over  the  second  joint  of  the 
finger,  and  an  inflating  bulb.  The 
same  apparatus  may  be  used  as  by  the 
Riva-Rocci  method,  with  the  substitu- 
tion of  the  ring  for  the  finger,  in  the 
place  of  the  bag  for  the  arm. 

Ereanger's  Sphygmomanometer. 
—  (See  Howell's  Physiology,  p.  456,, 
Fig.  191  and  192.)  This  instrument 
records  systolic  and  diastolic  pres- 
sures. The  mercury  manometer,  arm 
piece  and  inflating  bulb,  are  the  same  as  for  the  Riva-Rocci. 
In  addition  to  this  the  arm  piece  is  in  communication  with 
a  rubber  bulb,  which  is  enclosed  in  a  glass  bulb,  which  is 
connected  with  a  recording  tambour.  The  tambour  records 
the  fluctuations  in  pressure.  Two  forms  of  the  apparatus 
exist  in  the  laboratory,  differing  essentially  in  the  stop- 
cocks used  to  govern  the  flow  of  the  air.  These  are 
described  on  cards  accompanying  the  instruments. 


J'igr- 36.  Laboratory 
form  of  Riva-Rocci  in- 
strument. A,  reservoir  of 
niercurj';  B,  capillary 
manometer  tube;  C,  tube 
connecting  with  rubber 
cufTonarm  (or  in  the  case 
of  the  Gaertner  experi- 
ment, with  the  pneumatic 
ring);  D,  rubber  bulb;  E, 
outlet  tube;  F,  vertical 
tube,  with  pin  hole  in  the 
cap. 


HUMAN   BLOOD  PRESSURE.  I  75 

Experiment. — Each  student  is  to  determine  the  systolic 
pressure  of  his  associate  with  the  Riva-Rocci,  Gaertner,  and 
Erlanger  instruments,  and  the  diastolic  pressure  with  the 
Erlanger  apparatus,  under  the  following  conditions : 

1.  From  the  right  arm  in  the  sitting  position. 

2.  From  the  left  arm  in  the  sitting  position  (the  usual 
method). 

3.  From  the  left  arm,  standing,  with  arm  supported 
on  table. 

4.  From  left  arm,  lying  down. 

In  the  sitting  position,  the  subject's  arm  is  to  be  placed, 
extended,  on  the  table,  on  a  level  with  his  heart.  In  order 
to  take  the  required  number  of  observations,  the  student 
must  thoroughl}-  understand  the  instruments  and  the  method 
of  work,  and  have  practiced  taking  the  pulse  in  a  number 
of  preliminary  tests.  The  results  should  be  systematically 
tabulated,  and  a  suitable  table  for  entering  them  should 
be  prepared  before  making  the  observations. 

a.     The  Systolic  Pressure. 

1.  Gaertner's  Tonometer. — Apply  an  Esmarch  band- 
age to  the  finger.  Connect  the  tube  from  finger  ring  or  bag 
with  the  Riva-Rocci  manometer.  Using  the  bulb,  carefully 
raise  the  pressure  to  130  mm.  Now  turn  the  stop-cock  so 
as  to  shut  the  inflating  bulb  ofif  from  the  manometer. 
Remove  the  bandage.  The  falling  pressure  as  indicated 
by  the  manometer  can  be  controlled  by  placing  the  finger 
over  the  leak  in  the  top  of  the  vertical  tube  (F).  Read  the 
pressure  when  the  formerly  bloodless  extremity  of  the 
finger  first  begins  to  flush  and  become  cyanotic  with  the 
returning  blood. 

2.  The  Riva-Rocci  Sphygmomanometer. — Connect 
the  arm  bag  with  this  instrument.  While  feeling  the  sub- 
ject's pulse  with  the  fingers  of  the  right  hand,  with  the  left 
raise  the  pressure  in  the  manometer  to  about  150  mm. 
Controlling  the  leak  as  before,  read  the  pressure  at  the 
instant  the  return  of  the  pulse  is  felt.  Caution. — Do  not 
.lustake  the  pulse  in  your  own  fingers  for  that  of  the  subject 

13 


176  EXPERIMENT    XXXI. 

3.  The  Erlanger  Sphygmomanometer.  —  Having 
connected  this  instrument  with  the  cuff  on  the  arm,  proceed 
as  before  and  read  the  pressure  at  the  instant  of  the  return 
of  the  pulse.  The  danger  of  error  from  feeling  the  pulse 
in  one's  own  finger  tips,  is  slight  if  one  notes  that  the  pulse 
which  is  felt  coincides  with  the  pulsations  of  the  tambour 
attached  to  the  glass  bulb. 

b.     The  Diastolic  Pressure. 

The  Erlanger  Sphygmomanometer. — See  that  tam- 
bour lever  writes  lightly  upon  the  drum.  Raise  pressure 
to  about  100  mm.,  then  allow  it  to  fall  to  90  mm.  Shut  off 
the  leak  and  record  on  the  drum  a  series  of  at  least  15  pulse 
beats  at  this  pressure.  Now  start  the  drum,  open  leak  "and 
allow  pressure  to  fall  10  mm.,  close  off  leak  and  record 
another  series  of  15  pulse  waves.  Continue  after  this  man- 
ner until  the  height  of  the  pulsations  decreases  markedly. 
Be  careful  to  mark  on  record  the  pressure  at  which  each 
series  of  pulsations  was  obtained. 

"After  a  certain  level  (in  normal  pulses  25  to  40  mm. 
below  the  systolic  pressure)  the  extent  of  the  oscillations 
diminishes  rapidly.  The  lowest  point  at  which  it  remains 
maximal  is  the  diastolic  lateral  pressure."     (Sahli.) 


HUMAN  BLOOD  PRESSURE.  .  177 


178 


F.XriiRrMJCNT    XXXI. 


NORMAL  SOUNDS  OF   ilKAKT. 


179 


EXPERIMENT  XXXII. 

The  Normal  Sounds  of  the  Heart. 

The  normal  heart  sounds  may  be  heard  with  the  unaided 
ear,   but   the    stethoscope   is   commonly    used.      It   consists 


Fig.  37.  Diagram  showing  position  of  heart  in  cliest,  position  of  valves  as 
projected  on  the  wall  of  the  chest,  and  the  parts  of  the  chest  where  the  sounds 
of  the  heart  are  heard  best.  M.  position  of  apex  beat,  and  sound  from  mitral 
valve;  T,  sound  from  tricuspid  valve;  A,  sound  from  aortic  valve;  P,  sound  from 
pulmonary  valve. 

essentially  of  a  receiving  disk  and  a  pair  of  ear-tubes,  con- 
nected with  tubing.  It  aids  by  multiplication  of  the  sound 
and  by   excluding  outside   sounds.     Distracting  noises,   to 


l80  EXPERIMENT   XXXII. 

be  avoided,  are  apt  to  ari^-  f'-^'n  (.1}  rubbing  of  tubes 
aa^rxi«ot  ca.x,ii  other  or  against  clothing,  (2)  breathing  by  the 
listener  upon  the  metal  spring  holding  the  ear-tubes,  (3) 
movement  of  the  receiving  disk  upon  the  skin,  (4)  move- 
ments or  breath  sounds  of  the  subject,  and  (5)  talking 
b\  either  subject  or  listeners.  The  multiple  instrument 
enables  several  persons  to  hear  the  same  sound  at  once,  and 
therefore  is  useful  in  teaching.  The  ear  tubes  should  be 
cleansed  before  inserting  them  for  the  fint  time,  to  avoid 
possible  infection.  The  tubes  are  placed  in  the  ears  with 
the  tips  pointing  inward  and  upward.  The  receiving  disk 
is  held  firmly  against  the  skin.  Avoid  kinks  in  the  rubber 
tubes. 

The  diagram  shows  the  position  of  the  heart  in  the 
chest,  and  the  letters.  A,  P,  T,  and  M  mark  the  areas 
where  the  disk  is  placed  in  listening  to  the  separate  valve 
sounds.  Each  letter  is  connected  by  a  dotted  line  with  a 
dark  spot  showing  the  position  of  the  corresponding  valves. 
These  four  areas,  known  as  the  aortic,  pulmonary,  tricuspid, 
and  mitral  areas,  are  so  named  because  the  sounds  made 
by  the  closure  of  the  valves  named  are  heard  best  in  those 
places,  but  it  must  be  remembered  that  no  one  of  the  valve 
sounds  can  be  isolated  at  any  point,  but  that  all  enter  into 
the  composite  sounds  heard  at  each  area.  Tt  is  the  relative 
loudness  of  particular  sounds  that  give  the  areas  the  names 
which  they  bear. 

(T.     Ausc\dtatio)i  oi'cr  the  Loiiter  Part  of  the  Chest. 

One  student  of  the  group  is  chosen  as  subject,  and  he 
seats  himself  in  a  chair,  the  others  seating  themselves 
closely  around  him.  The  receiving  disk  is  first  applied 
over  the  mitral  area,  viz.  at  the  point  where  the  apex 
beat  is  felt,  in  the  5th  intercostal  space,  slightly  within  the 
nipple  line.  With  the-  disk  in  this  position,  listen  to  the 
licart  sounds  for  several  minutes.  Observe  ( i )  the  two 
distinct  sounds  with  a  very  short  interval  between  them, 
(2)  the  greater  loudness  of  the  first  sound,  (3)  the  boom- 
ing character  of  the  first  sound  contrasted  with  the  sharp 
click  of  the  second.  The  first  sound,  which  marks  the 
beginning  of  the   systole  of  the   ventricle,   is  a  compound 


NORMAL  SOUNDS  OF   HEART.  l8l 

sound,  composed  of  the  click  caused  by  the  closure  of  the 
two  auriculo-ventricular  valves,  the  sound  made  by  the 
contraction  of  the  muscular  substance  of  the  two  ventricles, 
and  by  the  vibrations  of  the  suddenly  tensed  chordae  ten- 
dineae.  The  muscular  element  which  prolongs  the  sound 
into  the  period  of  systole,  helps  to  give  it  the  booming 
character.  Normally  the  two  ventricles  contract  together, 
and  the  mitral  and  tricuspid  valves  close  at  the  same 
instant,  so  that  the  action  of  the  two  sides  of  the  heart 
is  represen'.ed  by  a  single  sound.  Compare  it  with 
the  sound  heard  by  placing  the  disk  of  the  stethoscope 
on  the  muscle  of  the  forearm  and  causing  it  to  con- 
tract rhythmically.  The  second  sound  is  produced  by 
the  closure  of  the  aortic  and  pulmonary  semi-lunar 
valves,  which  normally  close  at  the  same  time.  Now 
apply  the  disk  over  the  tricuspid  area  and  observe  ( i )  the 
greater  prominence  of  the  valve  sound  and  lessened  muscle 
sound,  (2)  the  clear  and  high  pitched  quality  of  the  sound, 
(3)  the  comparative  loudness  of  the  first  sound  as  before, 
and  (4)  the  rhythm,  which  is  also  the  same  as  in  the 
mitral  area.  Change  the  disk  quickly  from  one  of  these 
two  areas  to  the  other,  so  as  to  bring  out  distinctly  the 
differences  in  the  sounds.  Apply  it  at  intermediate  points 
and  observe  how  the  characteristic  sounds  of  one  area  grad- 
ually shade  off  into  those  of  the  other. 

b.     Ausciiltafioii  over  the  Base  of  the  Heart. 

Apply  the  disk  over  the  aortic  area  and  observe  ( i )  the 
greater  loudness  of  the  second  sound  as  compared  with 
the  first,  (2)  almost  complete  absence  of  booming  muscle 
sound,  (3)  the  same  rhythm  as  before.  The  sounds  heard 
here  are  mostly  valvular,  and  the  aortic  sounds  predominate. 
Listen  in  same  manner  at  pulmonary  area,  and  compare 
the  sounds  heard  in  aortic  and  pulmonary  areas.  Listen  at 
points  intervening  between  mitral  and  aortic  areas.  Change 
the  disk  quickly  between  the  four  areas,  and  let  the  listeners 
try  to  recognize  the  area  by  the  sounds  heard.  L"se  each 
student  as  subject  in  turn. 

In  diagnosis  it  is  often  necessary  to  locate  an  abnormal 
sound    in    relation    to   the     pulse    beat    and    thence    to   the 


102  EXPERIMENT   XXXII. 

heart  cycle.  The  first  sound,  produced  by  contraction  of 
heart  muscle  and  closure  of  auriculo-ventricular  valves,  is 
evidently  systolic.  The  second  sound,  made  by  closure  of 
semilunar  valves,  is  evidently  diastolic.  Therefore,  any 
sound  occurring  between  the  beginning  of  the  first  and  the 
beginning  of  the  second  normal  sounds  must  be  systolic, 
and  any  sound  occurring  between  the  beginning  of  the  sec- 
ond sound  and  the  beginning  of  the  first  sound  of  the  next 
cycle  must  be  diastolic. 

c.     Time  Relations  of  Heart  Sounds  and  Pulse. 

Experiment.— Record  the  radial  and  carotid  pulse  on 
a  drum  along  with  a  signal  connected  with  a  cell  and  Morse 
key.  Listen  to  heart  sounds  and  let  one  listener  so  work  the 
key  that  the  click  of  the  signal  shall  exactly  coincide  with 
the  heart  sounds.  When  he  is  able  to  do  this  well,  as  tested 
by  all  the  listeners,  run  drum  at  fast  speed  and  record  the 
time  of  the  sounds  in  relation  with  the  two  pulse  curves. 
The  reaction  time  to  sound  varies  from  0.15-0.20  sec, 
according  to  the  observer,  hence  to  have  the  sound  of  the 
heart  and  the  signal  coincide,  the  experimenter  will  have 
to  anticipate  the  beat,  i.  e.,  determine  the  rhythm  by  listen- 
ing a  short  time  and  then  tap  at  the  instant  that  the  beats 
are  to  be  expected.  Exact  results  cannot  be  obtained 
because  there  will  be  slight  errors  of  judgment  on  the  part 
of  the  experimenter,  and  because  the  rate  of  the  heart  varies 
somewhat  with  the  respiration.  Nevertheless,  if  care  be 
used,  a  good  picture  of  the  relative  time  of  the  coming  of 
the  sounds  of  the  heart  and  of  the  carotid  and  radial  pulse 
can  be  obtained. 

Notice  that  the  first  sound  slightly  precedes  the  primary 
upstroke  of  the  carotid  pulse  (about  .01  sec),  and  that  the 
second  sound  slightly  precedes  the  dicrotic  wave.  Also 
observe  that  the  primary  wave  of  the  radial  pulse  begins 
about  half  way  between  the  two  heart  sounds.  It  is  evident, 
therefore,  that  the  place  of  any  sound  of  doubtful  nature 
can  be  located  rather  definitely  in  the  cycle  by  its  relation 
to  the  carotid  pulse,  but  not  so  well  by  reference  to  the 
radial. 


NORMAIv  SOUNDS  OF   HEART.  I83 


l84  EXPERIMENT  XXXII. 


INFLUENCES   AFFKcriNG    RESPIRATION.  185 

EXPERIMENT  XXXIII. 

Thoracic    and    Abdominal    Movements    in    Respiration. 

Apparatus. — Mount  two  recording  tambours  and  a 
time  signal  to  write  in  a  vertical  line  ;  connect  the  signal  to 
clock  circuit ;  connect  the  two  tambours  with  special  rubber 
lubes  to  two  pneumographs,  leaving  side  tubes  open. 

Experiment. — The  subject  seats  himself  comfortably, 
then  the  cord  of  one  pneumograph  is  passed  around  his 
chest  and  the  cord  of  the  other  around  his  waist.  Tie  them 
with  a  tension  that  will  extend  the  pneumographs  about 
2  cm.  Subject  should  sit  so  as  not  to  see  the  curves  and 
should  pay  as  little  attention  to  breathing  as  possible. 

a.  Xonnal  Record. 

After  subject  has  remained  quietly  seated  for  at  least 
two  minutes,  place  clips  on  side  tubes,  start  drum  at  2  mm. 
per  second  and  record  curves  for  one  minvite.  N^atural. 
unconscious  breathing  is  what  we  wish  to  study,  and  hence 
the  subject  should  try  to  think  of  something  else. 

b.  Effect  of  Using  the  J^oicc. 

Record  normal  curves  for  10  seconds,  then  read  aloud 
for  30  seconds.  In  same  manner  try  the  effect  of  counting 
aloud  in  unison  with  the  ticking  of  the  clock.  Alwaj'^ 
mark  on  curve  the  time  when  each  test  begins  and  ends, 
and  what  was  done.  Note  the  effects  on  rate  and  character 
of  the  movements. 

c.  Inhibitory  Effects  of  S-a'alloiciug. 

Take  normal  record  for  15  seconds,  then  let  subject 
drink  a  glass  of  water  without  stopping,  taking  record  dur- 
ing the  drinking  and  for  15  seconds  after. 

(/.     Effects  of  Effort. 

In  the  same  manner  observe  the  effect  of  trying  to  hold 
two  pin  points  as  close  together  as  possible  without  touching. 


l86  EXPERIMENM'  xmxiu. 

for  20  seconds  ;  of  clenching;  the  fists  as  tightly  as  possible  for 
20  seconds ;  of  clenching  the  fists  as  rapidly  as  possible  for 
20  seconds  ;  of  pressing  the  hands  upon  the  knees  strongly 
for  20  seconds. 

Note  the  effect  in  the  dift'erent  cases,  and  explain  the 
difference. 

e.     Relation  of  Rate  of  Respiration  to  Rate  of  Heart 

Replace  the  abdominal  pneumograph  by  a  carotid  tam- 
bour ;  then  study  the  following  cases : 

( T )  Relative  rates  under  normal  conditions,  sitting 
quietly. 

(2)  Effect  of  adding  a  column  of  20  or  more  figures 
rapidly. 

(3)  Eff'ect  of  recalling  exciting  experiences. 

It  is  of  course  evident  that  voluntary  control  of  the 
rate  of  breathing  in  all  of  the  foregoing  tests  lessens  their 
value.  Usually  it  is  only  in  the  later  tests,  after  the  subject 
has  become  accustomed  to  wearing  the  apparatus,  and 
the  work  has  ceased  to  be  interesting,  that  the  subject  will 
breathe  naturally.  It  is  best,  for  this  reason  for  all  the 
tests  to  be  made  first  on  one  student  and  later  on  his  asso- 
ciate. 


JNl'I.UKNCES   AFFivCTINC   RESPIRATION.  187 


l88  EXPERIMENT  XXXll). 


JU/V  22 


t92d 


